Drugs Details

Drugs Info of Zanaflex
Drugs Details
  • Drugs Type  : Multum
  • Date : 9th Jul 2015 06:49 am
  • Brand Name : Zanaflex
  • Generic Name : tizanidine (Pronunciation: tye ZAN i deen)
Descriptions

Zanaflex® (tizanidine hydrochloride) is a central alpha2-adrenergic agonist. Tizanidine HCl is a white to off-white, fine crystalline powder, which is odorless or with a faint characteristic odor. Tizanidine is slightly soluble in water and methanol; solubility in water decreases as the pH increases. Its chemical name is 5-chloro-4-(2- imidazolin-2-ylamino)-2,1,3-benzothiadiazole monohydrochloride. Tizanidine's molecular formula is C9H8ClN5S-HCl, its molecular weight is 290.2 and its structural formula is:

 

ZANAFLEX Capsules® (tizanidine hydrochloride) Structural Formula Illustration

 

Zanaflex Capsules® are supplied as 2, 4, and 6 mg capsules for oral administration. Zanaflex Capsules® contain the active ingredient, tizanidine hydrochloride (2.29 mg equivalent to 2 mg tizanidine base, 4.58 mg equivalent to 4 mg tizanidine base, and 6.87 mg equivalent to 6 mg tizanidine base), and the inactive ingredients, hypromellose, silicon dioxide, sugar spheres, titanium dioxide, gelatin, and colorants.

Zanaflex® tablets are supplied as 4 mg tablets for oral administration. Zanaflex® tablets contain the active ingredient, tizanidine hydrochloride (4.58 mg equivalent to 4 mg tizanidine base), and the inactive ingredients, colloidal silicon dioxide, stearic acid, microcrystalline cellulose and anhydrous lactose.

 

What are the possible side effects of tizanidine (Zanaflex)?

Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have any of these serious side effects:

  • feeling light-headed, fainting, slow heart rate;
  • hallucinations, confusion, unusual thoughts or behavior;
  • nausea, stomach pain, low fever, loss of appetite, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes); or
  • burning or pain when you urinate.

Less serious side effects may be more...

Read All Potential Side Effects and See Pictures of Zanaflex »

What are the precautions when taking tizanidine (Zanaflex)?

Before taking tizanidine, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

Before using this medication, tell your doctor or pharmacist your medical history, especially of: low blood pressure, kidney disease, liver disease.

This drug may make you dizzy or drowsy. Do not drive, use machinery, or do any activity that requires alertness until you are sure you can perform such activities safely. Avoid alcoholic beverages.

Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal...

Read All Potential Precautions of Zanaflex »

Indications

Zanaflex is a central alpha-2-adrenergic agonist indicated for the management of spasticity. Because of the short duration of therapeutic effect, treatment with Zanaflex should be reserved for those daily activities and times when relief of spasticity is most important [see DOSAGE AND ADMINISTRATION].

Dosage Administration

Dosing Information

Zanaflex Capsules® or Zanaflex® tablets may be prescribed with or without food. Once the formulation has been selected and the decision to take with or without food has been made, this regimen should not be altered.

Food has complex effects on tizanidine pharmacokinetics, which differ with the different formulations. Zanaflex Capsules and Zanaflex tablets are bioequivalent to each other under fasting conditions (more than 3 hours after a meal), but not under fed conditions (within 30 minutes of a meal). These pharmacokinetic differences may result in clinically significant differences when switching administration of tablet and capsules and when switching administration between the fed or fasted state. These changes may result in increased adverse events, or delayed or more rapid onset of activity, depending upon the nature of the switch. For this reason, the prescriber should be thoroughly familiar with the changes in kinetics associated with these different conditions [see CLINICAL PHARMACOLOGY].

The recommended starting dose is 2 mg. Because the effect of Zanaflex peaks at approximately 1 to 2 hours post-dose and dissipates between 3 to 6 hours post-dose, treatment can be repeated at 6 to 8 hour intervals, as needed, to a maximum of three doses in 24 hours.

Dosage can be gradually increased by 2 mg to 4 mg at each dose, with 1 to 4 days between dosage increases, until a satisfactory reduction of muscle tone is achieved. The total daily dose should not exceed 36 mg. Single doses greater than 16 mg have not been studied.

Dosing in Patients with Renal Impairment

Zanaflex should be used with caution in patients with renal insufficiency (creatinine clearance < 25 mL/min), as clearance is reduced by more than 50%. In these patients, during titration, the individual doses should be reduced. If higher doses are required, individual doses rather than dosing frequency should be increased [see WARNINGS AND PRECAUTIONS].

Dosing in Patients with Hepatic Impairment

Zanaflex should be used with caution in patients with any hepatic impairment. In these patients, during titration, the individual doses should be reduced. If higher doses are required, individual doses rather than dosing frequency should be increased. Monitoring of aminotransferase levels is recommended for baseline and 1 month after maximum dose is achieved, or if hepatic injury is suspected. [see Use In Specific Populations]

Drug Discontinuation

If therapy needs to be discontinued, particularly in patients who have been receiving high doses (20 mg to 36 mg daily) for long periods (9 weeks or more) or who may be on concomitant treatment with narcotics, the dose should be decreased slowly (2 mg to 4 mg per day) to minimize the risk of withdrawal and rebound hypertension, tachycardia, and hypertonia [seeDrug Abuse and Dependence].

How Supplied

Dosage Forms And Strengths

Capsules
  • 2 mg: Light blue opaque body with a light blue opaque cap with “2 MG” printed on the cap
  • 4 mg: White opaque body with a blue opaque cap with “4 MG” printed on the cap
  • 6 mg: Blue opaque body with a white stripe and blue opaque cap with “6 MG” printed on the cap
Tablets
  • 4 mg white, uncoated tablets with a quadrisecting score on one side and debossed with “A594” on the other side

Storage And Handling

Zanaflex Capsules®

Zanaflex Capsules® (tizanidine hydrochloride) capsules are available in three strengths as two-piece hard gelatin capsules containing tizanidine hydrochloride 2.29 mg, 4.58 mg and 6.87 mg, equivalent to 2 mg, 4 mg and 6 mg tizanidine base.

  • The 2 mg capsules have a light blue opaque body with a light blue opaque cap with “2 MG” printed on the cap: bottles of 150 capsules (NDC 10144-602-15)
  • The 4 mg capsules have a white opaque body with a blue opaque cap with “4 MG” printed on the cap: bottles of 150 capsules (NDC 10144-604-15)
  • The 6 mg capsules have a blue opaque body with a white stripe and blue opaque cap with “6 MG” printed on the capsules: bottles of 150 capsules (NDC -10144-606-15)

Store at 25°C (77°F); excursions permitted to 15–30°C (59–86°F) [see USP Controlled Room Temperature]. Dispense in containers with child resistant closure.

Zanaflex® Tablets

Zanaflex® (tizanidine hydrochloride) tablets are available as 4 mg white, uncoated tablets containing tizanidine hydrochloride 4.58 mg, equivalent to 4 mg tizanidine base. The tablets have a quadrisecting score on one side and are debossed with “A594” on the other side. Tablets are provided as follows: bottles of 150 tablets (NDC -10144-594-15).

Store at 25°C (77°F); excursions permitted to 15–30°C (59–86°F) [see USP Controlled Room Temperature].

Dispense in containers with child resistant closure .

Marketed and Distributed by: Acorda Therapeutics Inc. Ardsley, NY 10502. Revised: November 2013.

Side Effects

The following adverse reactions are described elsewhere in other sections of the prescribing information:

  • Hypotension [see WARNINGS AND PRECAUTIONS]
  • Liver Injury [see WARNINGS AND PRECAUTIONS]
  • Sedation [see WARNINGS AND PRECAUTIONS]
  • Hallucinosis/Psychotic-Like Symptoms [see WARNINGS ANDPRECAUTIONS]
  • Hypersensitivity Reactions [see WARNINGS AND PRECAUTIONS]

Clinical Trials Experience

Because clinical studies are conducted under widely varying conditions,adverse reaction rates observed in the clinical studies of a drug cannot be directly compared to rates in the clinical studies of another drug and may not reflect the rates observed in clinical practice.

Three double-blind, randomized, placebo controlled -clinical studies were conducted to evaluate the effect of tizanidine on spasticity control. Two studies were conducted in patients with multiple sclerosis and one in patients with spinal cord injury. Each study had a 13-week active treatment period which included a 3-week titration phase to the maximum tolerated dose up to 36 mg/day in three divided doses, a 9-week plateau phase where the dose of tizanidine was held constant and a 1- week dose tapering. In all, 264 patients received tizanidine and 261 patients received placebo. Across the three studies patient ages ranged from 15–69 years and 51.4 percent were women. The median dose during the plateau phase ranged from 20–28 mg/day.

The most frequent adverse reactions reported in multiple dose, placebo-controlled clinical studies involving 264 patients with spasticity were dry mouth, somnolence/sedation, asthenia (weakness, fatigue and/or tiredness) and dizziness. Three-quarters of the patients rated the events as mild to moderate and one-quarter of the patients rated the events as being severe. These events appeared to be dose related.

Table 1 lists signs and symptoms that were reported in greater than 2% of patients in three multiple dose, placebo-controlled studies who received Zanaflex where the frequency in the Zanaflex group was greater than the placebo group. For comparison purposes, the corresponding frequency of the event (per 100 patients) among placebo treated patients is also provided.

Table 1: Multiple Dose, Placebo-Controlled Studies—Frequent ( > 2%) Adverse Reactions Reported for Which Zanaflex Tablets Incidence is Greater than Placebo

EVENT PLACEBO 
N = 261 
%
ZANAFLEX TABLET 
N = 264
%
Dry mouth 10 49
Somnolence 10 48
Asthenia* 16 41
Dizziness 4 16
UTI 7 10
Infection 5 6
Constipation 1 4
Liver test abnormality 2 6
Vomiting 0 3
Speech disorder 0 3
Amblyopia (blurred vision) < 1 3
Urinary frequency 2 3
Flu syndrome 2 3
Dyskinesia 0 3
Nervousness < 1 3
Pharyngitis 1 3
Rhinitis 2 3
*(weakness, fatigue, and/or tiredness)

 

In the single dose, placebo-controlled study involving 142 patients with spasticity due to multiple sclerosis (Study 1) [see Clinical Studies], the patients were specifically asked if they had experienced any of the four most common adverse reactions: dry mouth, somnolence (drowsiness), asthenia (weakness, fatigue and/or tiredness) and dizziness. In addition, hypotension and bradycardia were observed. The occurrence of these reactions is summarized in Table 2. Other events were, in general, reported at a rate of 2% or less.

Table 2: Single Dose, Placebo-Controlled Study—Common Adverse Reactions Reported

EVENT PLACEBO
N = 48
%
ZANAFLEX TABLET, 8MG, 
N = 45
%
ZANAFLEX TABLET, 16 MG, 
N = 49
%
Somnolence 31 78 92
Dry mouth 35 76 88
Asthenia* 40 67 78
Dizziness 4 22 45
Hypotension 0 16 33
Bradycardia 0 2 10
*(weakness, fatigue, and/or tiredness)

 

Post-Marketing Experience

The following adverse reactions have been identified during post approval use of Zanaflex. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure.

Certain events, such as somnolence, dry mouth, hypotension, decreased blood pressure, bradycardia, dizziness, weakness or asthenia, muscle spasms, hallucinations, fatigue, liver function test abnormality and hepatotoxicity, have been observed in post marketing and clinical trials and are discussed in previous sections of this document.

The following adverse reactions have been identified as occurring in the post marketing experience of Zanaflex. Based on the information provided regarding these reactions, a causal relationship with Zanaflex cannot be entirely excluded. The events are listed in order of decreasing clinical significance; severity in the post marketing setting is not reported.

  • Stevens Johnson Syndrome
  • Anaphylactic Reaction
  • Exfoliative Dermatitis
  • Ventricular Tachycardia
  • Hepatitis
  • Convulsion
  • Depression
  • Arthralgia
  • Paresthesia
  • Rash
  • Tremor

Interactions

Fluvoxamine

Concomitant use of fluvoxamine and Zanaflex is contraindicated. Changes in pharmacokinetics of tizanidine when administered with fluvoxamine resulted in significantly decreased blood pressure, increased drowsiness, and increased psychomotor impairment. [see CONTRAINDICATIONS and CLINICAL PHARMACOLOGY]

Ciprofloxacin

Concomitant use of ciprofoxacin and Zanaflex is contraindicated. Changes in pharmacokinetics of tizanidine when administered with ciprofloxacin resulted in significantly decreased blood pressure, increased drowsiness, and increased psychomotor impairment [See CONTRAINDICATIONS andCLINICAL PHARMACOLOGY]

CYP1A2 Inhibitors other than Fluvoxamine and Ciprofloxacin

Because of potential drug interactions, concomitant use of Zanaflex with other CYP1A2 inhibitors, such as zileuton, fluoroquinolones other than strong CYP1A2 inhibitors (which are contraindicated), antiarrythmics (amiodarone, mexiletine, propafenone, and verapamil), cimetidine, famotidine, oral contraceptives, acyclovir, and ticlopidine) should be avoided. If their use is clinically necessary, therapy should be initiated with 2 mg dose and increased in 2–4 mg steps daily based on patient response to therapy. If adverse reactions such as hypotension, bradycardia, or excessive drowsiness occur, reduce or discontinue Zanaflex therapy. [see WARNINGS AND PRECAUTIONS and CLINICAL PHARMACOLOGY]

Oral Contraceptives

Concomitant use of Zanaflex with oral contraceptives is not recommended. However, if concomitant use is clinically necessary, initiate Zanaflex with a single 2 mg dose and increase in 2–4 mg steps daily based on patient response to therapy. If adverse reactions such as hypotension, bradycardia, or excessive drowsiness occur, reduce or discontinue Zanaflex therapy. [seeCLINICAL PHARMACOLOGY]

Alcohol

Alcohol increases the overall amount of drug in the bloodstream after a dose of Zanaflex. This was associated with an increase in adverse reactions of Zanaflex. The CNS depressant effects of Zanaflex and alcohol are additive. [see CLINICAL PHARMACOLOGY]

Other CNS Depressants

The sedative effects of Zanaflex with CNS depressants (e.g.,benzodiazepines, opioids, tricyclic antidepressants) may be additive. Monitor patients who take Zanaflex with another CNS depressant for symptoms of excess sedation. [see CLINICAL PHARMACOLOGY]

α2-adrenergic agonists

Because hypotensive effects may be cumulative, it is not recommended that Zanaflex be used with other α2-adrenergic agonists. [see WARNINGS ANDPRECAUTIONS]

Drug Abuse And Dependence

Abuse

Abuse potential was not evaluated in human studies. Rats were able to distinguish tizanidine from saline in a standard discrimination paradigm, after training, but failed to generalize the effects of morphine, cocaine, diazepam, or phenobarbital to tizanidine.

Dependence

Tizanidine is closely related to clonidine, which is often abused in combination with narcotics and is known to cause symptoms of rebound upon abrupt withdrawal. Three cases of rebound symptoms on sudden withdrawal of tizanidine have been reported. The case reports suggest that these patients were also misusing narcotics. Withdrawal symptoms includedhypertension, tachycardia, hypertonia, tremor, and anxiety. Withdrawal symptoms are more likely to occur in cases where high doses are used, especially for prolonged periods, or with concomitant use of narcotics. If therapy needs to be discontinued, the dose should be decreased slowly to minimize the risk of withdrawal symptoms [see DOSAGE AND ADMINISTRATION].

Monkeys were shown to self-administer tizanidine in a dose-dependent manner, and abrupt cessation of tizanidine produced transient signs of withdrawal at doses > 35 times the maximum recommended human dose on a mg/m² basis. These transient withdrawal signs (increased locomotion, bodytwitching, and aversive behavior toward the observer) were not reversed bynaloxone administration.

Warnings

Included as part of the PRECAUTIONS section.

Precautions

Hypotension

Tizanidine is an α2-adrenergic agonist that can produce hypotension.Syncope has been reported in the post marketing setting. The chance of significant hypotension may possibly be minimized by titration of the dose and by focusing attention on signs and symptoms of hypotension prior to dose advancement. In addition, patients moving from a supine to fixed upright position may be at increased risk for hypotension and orthostatic effects.

Monitor for hypotension when Zanaflex is used in patients receiving concurrent antihypertensive therapy. It is not recommended that Zanaflex be used with other α2- adrenergic agonists. Clinically significant hypotension (decreases in both systolic and diastolic pressure) has been reported with concomitant administration of either fluvoxamine or ciprofloxacin and single doses of 4 mg of Zanaflex. Therefore, concomitant use of Zanaflex with fluvoxamine or with ciprofloxacin, potent inhibitors of CYP1A2, is contraindicated [see CONTRAINDICATIONS and DRUG INTERACTIONS].

Risk of Liver Injury

Zanaflex may cause hepatocellular liver injury. Zanaflex should be used with caution in patients with any hepatic impairment.. Monitoring ofaminotransferase levels is recommended for baseline and 1 month after maximum dose is achieved, or if hepatic injury is suspected. [see DOSAGE AND ADMINISTRATION and Use In Specific Populations]

Sedation

Zanaflex can cause sedation, which may interfere with everyday activity. In the multiple dose studies, the prevalence of patients with sedation peaked following the first week of titration and then remained stable for the duration of the maintenance phase of the study. The CNS depressant effects of Zanaflex with alcohol and other CNS depressants (e.g., benzodiazepines, opioids, tricyclic antidepressants) may be additive. Monitor patients who take Zanaflex with another CNS depressant for symptoms of excess sedation. [seeDRUG INTERACTIONS]

Hallucinosis/Psychotic-Like Symptoms

Zanaflex use has been associated with hallucinations. Formed, visual hallucinations or delusions have been reported in 5 of 170 patients (3%) in two North American controlled clinical studies. Most of the patients were aware that the events were unreal. One patient developed psychosis in association with the hallucinations. One patient among these 5 continued to have problems for at least 2 weeks following discontinuation of tizanidine. Consider discontinuing Zanaflex in patients who develop hallucinations.

Interaction with CYP1A2 Inhibitors

Because of potential drug interactions, Zanaflex is contraindicated in patients taking potent CYP1A2 inhibitors, such as fluvoxamine or ciprofloxacin. Adverse reactions such as hypotension, bradycardia, or excessive drowsiness can occur when Zanaflex is taken with other CYP1A2 inhibitors, such as zileuton, fluoroquinolones other than ciprofloxacin (which is contraindicated), antiarrythmics (amiodarone, mexiletine, propafenone), cimetidine, famotidine, oral contraceptives, acyclovir, and ticlopidine ). Concomitant use should be avoided unless the necessity for Zanaflex therapy is clinically evident. In such a case, use with caution. [see DRUG INTERACTIONS and CLINICAL PHARMACOLOGY]

Hypersensitivity Reactions

Zanaflex can cause anaphylaxis. Signs and symptoms including respiratory compromise, urticaria, and angioedema of the throat and tongue have been reported. Patients should be informed of the signs and symptoms of severe allergic reactions and instructed to discontinue Zanaflex and seek immediate medical care should these signs and symptoms occur. [seeCONTRAINDICATIONS]

Increased Risk of Adverse Reactions in Patients with Renal Impairment

Zanaflex should be used with caution in patients with renal insufficiency (creatinine clearance < 25 mL/min), as clearance is reduced by more than 50%. In these patients, during titration, the individual doses should be reduced. If higher doses are required, individual doses rather than dosing frequency should be increased. These patients should be monitored closely for the onset or increase in severity of the common adverse events (dry mouth, somnolence, asthenia and dizziness) as indicators of potential overdose. [see DOSAGE AND ADMINISTRATION and Use In Specific Populations]

Withdrawal Adverse Reactions

Withdrawal adverse reactions include rebound hypertension, tachycardia, and hypertonia. To minimize the risk of these reactions, particularly in patients who have been receiving high doses (20 to 28 mg daily) for long periods of time (9 weeks or more) or who may be on concomitant treatment with narcotics, the dose should be decreased slowly (2 to 4 mg per day). [seeDOSAGE AND ADMINISTRATION]

Nonclinical Toxicology

Carcinogenesis, mutagenesis, impairment of fertility

Carcinogenesis

Tizanidine was administered to mice for 78 weeks at oral doses up to 16 mg/kg/day, which is 2 times the maximum recommended human dose (MRHD) on a mg/m² basis. Tizanidine was administered to rats for 104 weeks at oral doses up to 9 mg/kg/day, which is 2.5 times the MRHD on a mg/m² basis. There was no increase in tumors in either species.

Mutagenesis

Tizanidine was negative in in vitro (bacterial reverse mutation [Ames] , mammalian gene mutation, and chromosomal aberration test in mammalian cells) and in vivo (bone marrow micronucleus, and cytogenetics) assay.

Impairment of fertility

Oral administration of tizanidine resulted in reduced fertility in male and female rats following doses of 30 and 10 mg/kg/day, respectively. No effect on fertility was observed at doses of 10 (male) and 3 (female) mg/kg/day, which are approximately 8 and 3 times, respectively, the MRHD on a mg/m² basis).

Use In Specific Populations

Pregnancy

Pregnancy Category C

Zanaflex has not been studied in pregnant women. Zanaflex should be given to pregnant women only if the benefit outweighs the risk to the unborn fetus. Reproduction studies performed in rats at a dose of 3 mg/kg, equal to the maximum recommended human dose on a mg/m² basis, and in rabbits at 30 mg/kg, 16 times the maximum recommended human dose on a mg/m² basis, did not show evidence of teratogenicity. Tizanidine at doses that are equal to and up to 8 times the maximum recommended human dose on a mg/m² basis increased gestation duration in rats. Prenatal and postnatal pup loss was increased and developmental retardation occurred. Post-implantation loss was increased in rabbits at doses of 1 mg/kg or greater, equal to or greater than 0.5 times the maximum recommended human dose on a mg/m² basis.

Nursing mothers

It is not known whether this drug is excreted in human milk. Because many drugs are excreted in human milk, caution should be exercised when Zanaflex is administered to a nursing woman.

Pediatric use

Safety and effectiveness in pediatric patients have not been established.

Geriatric use

Zanaflex is known to be substantially excreted by the kidney, and the risk of adverse reactions to this drug may be greater in patients with impaired renal function. Because elderly patients are more likely to have decreased renal function, care should be taken in dose selection, and it may be useful to monitor renal function. Clinical studies of Zanaflex did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently than younger subjects. Crossstudy comparison of pharmacokinetic data following single dose administration of 6 mg Zanaflex showed that younger subjects cleared the drug four times faster than the elderly subjects. In elderly patients with renal insufficiency (creatinine clearance < 25 mL/min), tizanidine clearance is reduced by more than 50% compared to healthy elderly subjects; this would be expected to lead to a longer duration of clinical effect. During titration, the individual doses should be reduced. If higher doses are required, individual doses rather than dosing frequency should be increased. Monitor elderly patients because they may have an increased risk for adverse reactions associated with Zanaflex.

Impaired Renal Function

Zanaflex is known to be substantially excreted by the kidney, and the risk of adverse reactions to this drug may be greater in patients with impaired renal function. In patients with renal insufficiency (creatinine clearance < 25 mL/min) clearance was reduced by more than 50%. In these patients, during titration, the individual doses should be reduced. If higher doses are required, individual doses rather than dosing frequency should be increased. These patients should be monitored closely for the onset or increase in severity of the common adverse events (dry mouth, somnolence, asthenia and dizziness) as indicators of potential overdose. [see DOSAGE AND ADMINISTRATION, WARNINGS AND PRECAUTIONS and CLINICAL PHARMACOLOGY]

Impaired Hepatic Function

The influence of hepatic impairment on the pharmacokinetics of tizanidine has not been evaluated. Because tizanidine is extensively metabolized in the liver, hepatic impairment would be expected to have significant effects on pharmacokinetics of tizanidine. [see DOSING AND ADMINISTRATION,WARNINGS AND PRECAUTIONS, and CLINICAL PHARMACOLOGY].

OverDose

A review of the safety surveillance database revealed cases of intentional and accidental Zanaflex overdose. Some of the cases resulted in fatality and many of the intentional overdoses were with multiple drugs including CNS depressants. The clinical manifestations of tizanidine overdose were consistent with its known pharmacology. In the majority of cases a decrease in sensorium was observed including lethargy, somnolence, confusion and coma. Depressed cardiac function is also observed including most oftenbradycardia and hypotension. Respiratory depression is another common feature of tizanidine overdose.

Should overdose occur, basic steps to ensure the adequacy of an airway and the monitoring of cardiovascular and respiratory systems should be undertaken. Tizanidine is a lipid-soluble drug, which is only slightly soluble in water and methanol. Therefore, dialysis is not likely to be an efficient method of removing drug from the body. In general, symptoms resolve within one to three days following discontinuation of tizanidine and administration of appropriate therapy. Due to the similar mechanism of action, symptoms and management of tizanidine overdose are similar to that following clonidine overdose. For the most recent information concerning the management of overdose, contact a poison control center.

ContrainDications

Zanaflex is contraindicated in patientstaking potent inhibitors of CYP1A2, such as fluvoxamine or ciprofloxacin [see DRUG INTERACTIONS].

Clinical Pharamacology

Mechanism of action

Tizanidine is a central alpha-2-adrenergic receptor agonist and presumably reduces spasticity by increasing presynaptic inhibition of motor neurons. The effects of tizanidine are greatest on polysynaptic pathways. The overall effect of these actions is thought to reduce facilitation of spinal motor neurons.

Pharmacokinetics

Absorption and Distribution

Following oral administration, tizanidine is essentially completely absorbed. The absolute oral bioavailability of tizanidine is approximately 40% (CV = 24%), due to extensive first-pass hepatic metabolism. Tizanidine is extensively distributed throughout the body with a mean steady state volume of distribution of 2.4 L/kg (CV = 21%) following intravenous administration in healthy adult volunteers. Tizanidine is approximately 30% bound to plasma proteins.

Differences between Zanaflex Capsules® and Zanaflex® Tablets

Zanaflex Capsules® and Zanaflex® tablets are bioequivalent to each other under fasting conditions, but not under fed conditions. A single dose of either two 4 mg tablets or two 4 mg capsules was administered under fed and fasting conditions in an open label, four period, randomized crossover study in 96 human volunteers, of whom 81 were eligible for the statistical analysis. Following oral administration of either the tablet or capsule (in the fasted state), peak plasma concentrations of tizanidine occurred 1.0 hours after dosing with a half-life of approximately 2 hours. When two 4 mg tablets were administered with food, the mean maximal plasma concentration was increased by approximately 30%, and the median time to peak plasma concentration was increased by 25 minutes, to 1 hour and 25 minutes. In contrast, when two 4 mg capsules were administered with food, the mean maximal plasma concentration was decreased by 20%, the median time to peak plasma concentration was increased 2 to 3 hours. Consequently, the mean Cmax for the capsule when administered with food is approximately 66% the Cmax for the tablet when administered with food.

Food also increased the extent of absorption for both the tablets and capsules. The increase with the tablet (~30%) was significantly greater than with the capsule (~10%). Consequently when each was administered with food, the amount absorbed from the capsule was about 80% of the amount absorbed from the tablet. Administration of the capsule contents sprinkled on applesauce was not bioequivalent to administration of an intact capsule under fasting conditions. Administration of the capsule contents on applesauce resulted in a 15%–20% increase in Cmax and AUC of tizanidine and a 15 minute decrease in the median lag time and time to peak concentration compared to administration of an intact capsule while fasting.

Figure 1: Mean Tizanidine Concentration vs. Time Profiles For Zanaflex Tablets and Capsules (2 × 4 mg) Under Fasted and Fed Conditions

Mean Tizanidine Concentration vs. Time Profiles - Illustration

 

Metabolism and Excretion

Tizanidine has linear pharmacokinetics over the doses studied in clinical development (1–20 mg). Tizanidine has a half-life of approximately 2.5 hours (CV=33%). Approximately 95% of an administered dose is metabolized. The primary cytochrome P450 isoenzyme involved in tizanidine metabolism is CYP1A2. Tizanidine metabolites are not known to be active; their half-lives range from 20 to 40 hours.

Following single and multiple oral dosing of 14C-tizanidine, an average of 60% and 20% of total radioactivity was recovered in the urine and feces, respectively.

Special Populations

Age Effects

No specific pharmacokinetic study was conducted to investigate age effects. Cross study comparison of pharmacokinetic data following single dose administration of 6 mg Zanaflex showed that younger subjects cleared the drug four times faster than the elderly subjects. Zanaflex has not been evaluated in children. [see Use in Specific Populations]

Hepatic Impairment

The influence of hepatic impairment on the pharmacokinetics of tizanidine has not been evaluated. Because tizanidine is extensively metabolized in the liver, hepatic impairment would be expected to have significant effects on pharmacokinetics of tizanidine. Zanaflex is not recommended in this patient population [see Use in Specific Populations]

Renal Impairment

Tizanidine clearance is reduced by more than 50% in elderly patients with renal insufficiency (creatinine clearance < 25 mL/min) compared to healthy elderly subjects; this would be expected to lead to a longer duration of clinical effect. Zanaflex should be used with caution in renally impaired patients [seeWARNINGS AND PRECAUTIONS and Use In Specific Populations].

Gender Effects

No specific pharmacokinetic study was conducted to investigate gender effects. Retrospective analysis of pharmacokinetic data, however, following single and multiple dose administration of 4 mg Zanaflex showed that gender had no effect on the pharmacokinetics of tizanidine.

Race Effects

Pharmacokinetic differences due to race have not been studied.

Drug Interactions

CYP1A2 Inhibitors

The interaction between Zanaflex and either fluvoxamine or ciprofloxacin is most likely due to inhibition of CYP1A2 by fluvoxamine or ciprofloxacin. The effect of fluvoxamine on the pharmacokinetics of a single 4 mg dose of Zanaflex was studied in 10 healthy subjects. The Cmax, AUC, and half-life of tizanidine increased by 12- fold, 33-fold, and 3-fold, respectively. The effect of ciprofloxacin on the pharmacokinetics of a single 4 mg dose of Zanaflex was studied in 10 healthy subjects. The Cmax and AUC of tizanidine increased by 7-fold and 10-fold, respectively. [see CONTRAINDICATIONS]

Although there have been no clinical studies evaluating the effects of other CYP1A2 inhibitors on tizanidine, other CYP1A2 inhibitors, such as zileuton, other fluoroquinolones, antiarrythmics (amiodarone, mexiletine, propafenone and verapamil), cimetidine, famotidine oral contraceptives, acyclovir and ticlopidine, may also lead to substantial increases in tizanidine blood concentrations [see WARNINGS AND PRECAUTIONS].

In vitro studies of cytochrome P450 isoenzymes using human liver microsomes indicate that neither tizanidine nor the major metabolites are likely to affect the metabolism of other drugs metabolized by cytochrome P450 isoenzymes.

Oral Contraceptives

No specific pharmacokinetic study was conducted to investigate interaction between oral contraceptives and Zanaflex. Retrospective analysis of population pharmacokinetic data following single and multiple dose administration of 4 mg Zanaflex, however, showed that women concurrently taking oral contraceptives had 50% lower clearance of tizanidine compared to women not on oral contraceptives [see WARNINGS AND PRECAUTIONS].

Acetaminophen

Tizanidine delayed the Tmax of acetaminophen by 16 minutes. Acetaminophen did not affect the pharmacokinetics of tizanidine.

Alcohol

Alcohol increased the AUC of tizanidine by approximately 20%, while also increasing its Cmax by approximately 15%. This was associated with an increase in side effects of tizanidine. The CNS depressant effects of tizanidine and alcohol are additive.

Clinical Studies

Tizanidine's capacity to reduce increased muscle tone associated with spasticity was demonstrated in two adequate and well controlled studies in patients with multiple sclerosis or spinal cord injury (Studies 1 and 2).

Single-Dose Study in Patients with Multiple Sclerosis with Spasticity

In Study 1, patients with multiple sclerosis were randomized to receive single oral doses of drug or placebo. Patients and assessors were blind to treatment assignment and efforts were made to reduce the likelihood that assessors would become aware indirectly of treatment assignment (e.g., they did not provide direct care to patients and were prohibited from asking questions about side effects). In all, 140 patients received placebo, 8 mg or 16 mg of Zanaflex.

Response was assessed by physical examination; muscle tone was rated on a 5 point scale (Ashworth score), with a score of 0 used to describe normal muscle tone. A score of 1 indicated a slight spastic catch while a score of 2 indicated more marked muscle resistance. A score of 3 was used to describe considerable increase in tone, making passive movement difficult. A muscle immobilized by spasticity was given a score of 4. Spasm counts were also collected. Assessments were made at 1, 2, 3 and 6 hours after treatment. A statistically significant reduction of the Ashworth score for Zanaflex compared to placebo was detected at 1, 2 and 3 hours after treatment. Figure 2 below shows a comparison of the mean change in muscle tone from baseline as measured by the Ashworth scale. The greatest reduction in muscle tone was 1 to 2 hours after treatment. By 6 hours after treatment, muscle tone in the 8 and 16 mg Zanaflex groups was indistinguishable from muscle tone in placebo treated patients. Within a given patient, improvement in muscle tone was correlated with plasma concentration. Plasma concentrations were variable from patient to patient at a given dose. Although 16 mg produced a larger effect, adverse events including hypotension were more common and more severe than in the 8 mg group. There were no differences in the number of spasms occurring in each group.

Figure 2: Single Dose Study—Mean Change in Muscle Tone from Baseline as Measured by the Ashworth Scale ± 95% Confidence Interval (A Negative Ashworth Score Signifies an Improvement in Muscle Tone from Baseline)

Mean Change in Muscle Tone - Illustration

 

Seven-Week Study in Patients with Spinal Cord Injury with Spasticity

In a 7-week study (Study 2), 118 patients with spasticity secondary to spinal cord injury were randomized to either placebo or Zanaflex. Steps similar to those taken in the first study were employed to ensure the integrity of blinding.

Patients were titrated over 3 weeks up to a maximum tolerated dose or 36 mg daily given in three unequal doses (e.g., 10 mg given in the morning and afternoon and 16 mg given at night). Patients were then maintained on their maximally tolerated dose for 4 additional weeks (i.e., maintenance phase). Throughout the maintenance phase, muscle tone was assessed on the Ashworth scale within a period of 2.5 hours following either the morning or afternoon dose. The number of daytime spasms was recorded daily by patients.

At endpoint (the protocol-specified time of outcome assessment), there was a statistically significant reduction in muscle tone and frequency of spasms in the Zanaflex treated group compared to placebo. The reduction in muscle tone was not associated with a reduction in muscle strength (a desirable outcome) but also did not lead to any consistent advantage of Zanaflex treated patients on measures of activities of daily living. Figure 3 below shows a comparison of the mean change in muscle tone from baseline as measured by the Ashworth scale.

Figure 3: Seven Week Study—Mean Change in Muscle Tone 0.5–2.5 Hours After Dosing as Measured by the Ashworth Scale ± 95% Confidence Interval (A Negative Ashworth Score Signifies an Improvement in Muscle Tone from Baseline)

Mean Change in Muscle Tone - Illustration

Patient Information

Serious Drug Interactions

Advise patients they should not take Zanaflex if they are taking fluvoxamine or ciprofloxacin because of the increased risk of serious adverse reactions including severe lowering of blood pressure and sedation. Instruct patients to inform their physicians or pharmacists when they start or stop taking any medication because of the risks associated with interaction between Zanaflex and other medicines.

Zanaflex Dosing

Tell patients to take Zanaflex exactly as prescribed (consistently either with or without food) and not to switch between tablets and capsules. Inform patients that they should not take more Zanaflex than prescribed because of the risk of adverse events at single doses greater than 8 mg or total daily doses greater than 36 mg. Tell patients that they should not suddenly discontinue Zanaflex, because rebound hypertension and tachycardia may occur.

Effects of Zanaflex

Warn patients that they may experience hypotension and to be careful when changing from a lying or sitting to a standing position. Tell patients that Zanaflex may cause them to become sedated or somnolent and they should be careful when performing activities that require alertness, such as driving a vehicle or operating machinery. Tell patients that the sedation may be additive when Zanaflex is taken in conjunction with drugs (baclofen,benzodiazepines) or substances (e.g., alcohol) that act as CNS depressants. Remind patients that if they depend on their spasticity to sustain posture and balance in locomotion, or whenever spasticity is utilized to obtain increased function, that Zanaflex decreases spasticity and caution should be used.

Consumer Overview Uses

IMPORTANT: HOW TO USE THIS INFORMATION: This is a summary and does NOT have all possible information about this product. This information does not assure that this product is safe, effective, or appropriate for you. This information is not individual medical advice and does not substitute for the advice of your health care professional. Always ask your health care professional for complete information about this product and your specific health needs.

 

TIZANIDINE - ORAL

 

(tye-ZAN-i-deen)

 

COMMON BRAND NAME(S): Zanaflex

 

USES: This medication is used to treat muscle spasms caused by certain conditions (such as multiple sclerosis, spinal cord injury). It works by helping to relax the muscles.

 

HOW TO USE: Take this medication by mouth as directed by your doctor, usually every 6 to 8 hours.

The dosage is based on your medical condition, response to treatment, and other medications you may be taking. Be sure to tell your doctor and pharmacist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products). To reduce your risk of side effects, your doctor may direct you to start this medication at a low dose and gradually increase your dose. Follow your doctor's instructions carefully. Do not take more than 36 milligrams a day or more than 3 doses in a 24-hour period.

Your body will absorb this medication differently depending on whether you take it as a tablet or capsule, whether you take it with food or on an empty stomach, or if you sprinkle the contents of the capsule on food. Be sure to discuss with your doctor how to take this medication to determine the best way to take your dose, especially when changes to your dose are being considered or if your doctor prescribes a different form of tizanidine (such as tablet or capsule).

This medication may cause withdrawal reactions, especially if it has been used regularly for a long time or in high doses. In such cases, withdrawal symptoms (such as anxiety, tremor, increased blood pressure/heart rate/muscle tenseness) may occur if you suddenly stop using this medication. Do not stop taking this medication without consulting your doctor. To prevent withdrawal reactions, your doctor may reduce your dose gradually. Consult your doctor or pharmacist for more details, and report any withdrawal reactions immediately.

Tell your doctor if your condition does not improve or if it worsens.

Consumer Overview Side Effect

SIDE EFFECTS: Dry mouth, drowsiness, dizziness, lightheadedness, constipation, weakness, and tiredness may occur. If any of these effects persist or worsen, tell your doctor or pharmacist promptly.

To relieve dry mouth, suck (sugarless) hard candy or ice chips, chew (sugarless) gum, drink water, or use a saliva substitute.

To reduce the risk of dizziness and lightheadedness, get up slowly when rising from a sitting or lying position.

Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

Tell your doctor right away if you have any serious side effects, including: fainting, mental/mood changes (such as hallucinations), slow/irregular heartbeat, vision changes (such as blurred vision).

Tizanidine has infrequently caused very serious (rarely fatal) liver disease. Tell your doctor immediately if you develop symptoms of liver disease, including: persistent nausea/vomiting, severe stomach/abdominal pain, dark urine, yellowing eyes/skin.

A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US -

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

 

Read the Zanaflex (tizanidine) Side Effects Center for a complete guide to possible side effects

Learn More »
 

PRECAUTIONS: Before taking tizanidine, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

Before using this medication, tell your doctor or pharmacist your medical history, especially of: low blood pressure, kidney disease, liver disease.

This drug may make you dizzy or drowsy. Do not drive, use machinery, or do any activity that requires alertness until you are sure you can perform such activities safely. Avoid alcoholic beverages.

Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products).

Older adults may be more sensitive to the side effects of this drug, especially dizziness and drowsiness. These effects can increase the risk of falling.

During pregnancy, this medication should be used only when clearly needed. Discuss the risks and benefits with your doctor.

It is unknown if this drug passes into breast milk. Consult your doctor before breast-feeding.

Consumer Overview Missed Dose

DRUG INTERACTIONS: Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval.

Some products that may interact with this drug include: certain drugs to treat high blood pressure (alpha agonists such as clonidine, methyldopa).

Other medications can affect the removal of tizanidine from your body, which may affect how tizanidine works. Examples include birth control pills, ciprofloxacin, fluvoxamine, among others.

Tell your doctor or pharmacist if you are taking other products that cause drowsiness including alcohol, antihistamines (such as cetirizine, diphenhydramine), drugs for sleep or anxiety (such as alprazolam, diazepam, zolpidem), other muscle relaxants, and narcotic pain relievers (such as codeine).

Check the labels on all your medicines (such as allergy or cough-and-cold products) because they may contain ingredients that cause drowsiness. Ask your pharmacist about using those products safely.

 

OVERDOSE: If overdose is suspected, contact a poison control center or emergency room immediately. US residents can call their local poison control center at 1-800-222-1222. Canada residents can call a provincial poison control center. Symptoms of overdose may include: severe dizziness/drowsiness, confusion, slow/shallow breathing, fainting.

 

NOTES: Do not share this medication with others.

Laboratory and/or medical tests (such as blood pressure, liver function) should be performed periodically to monitor your progress or check for side effects. Consult your doctor for more details.

 

MISSED DOSE: If you miss a dose, take it as soon as you remember. If it is near the time of the next dose, skip the missed dose and resume your usual dosing schedule. Do not double the dose to catch up.

 

STORAGE: Store at room temperature away from light and moisture. Do not store in the bathroom. Keep all medications away from children and pets.

Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company.

 

Information last revised March 2014. Copyright(c) 2014 First Databank, Inc.

Patient Detailed Side Effect

Brand Names: Zanaflex

Generic Name: tizanidine (Pronunciation: tye ZAN i deen)

  • What is tizanidine (Zanaflex)?
  • What are the possible side effects of tizanidine (Zanaflex)?
  • What is the most important information I should know about tizanidine (Zanaflex)?
  • What should I discuss with my healthcare provider before taking tizanidine (Zanaflex)?
  • How should I take tizanidine (Zanaflex)?
  • What happens if I miss a dose (Zanaflex)?
  • What happens if I overdose (Zanaflex)?
  • What should I avoid while taking tizanidine (Zanaflex)?
  • What other drugs will affect tizanidine (Zanaflex)?
  • Where can I get more information?

What is tizanidine (Zanaflex)?

 

Tizanidine is a short-acting muscle relaxer. It works by blocking nerve impulses (pain sensations) that are sent to your brain.

Tizanidine is used to treat spasticity by temporarily relaxing muscle tone.

Tizanidine may also be used for purposes other than those listed in this medication guide.

Tizanidine 2 mg-PAR

oval, white, imprinted with R179

What are the possible side effects of tizanidine (Zanaflex)?

 

Get emergency medical help if you have any of thesesigns of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have any of these serious side effects:

  • feeling light-headed, fainting, slow heart rate;
  • hallucinations, confusion, unusual thoughts or behavior;
  • nausea, stomach pain, low fever, loss of appetite, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes); or
  • burning or pain when you urinate.

Less serious side effects may be more likely to occur, such as:

  • drowsiness or dizziness;
  • feeling anxious or nervous;
  • numbness or tingling;
  • stomach pain, diarrhea, constipation, vomiting;
  • fever;
  • dry mouth;
  • muscle weakness, back pain;
  • increased muscle tone or spasms; or
  • sweating or skin rash.

This is not a complete list of side effects and others may occur. Tell your doctor about any unusual or bothersome side effect. You may report side effects to FDA at 1-800-FDA-1088.

Read the Zanaflex (tizanidine) Side Effects Center for a complete guide to possible side effects

Learn More »
 

What is the most important information I should know about tizanidine (Zanaflex)?

 

Tizanidine is a short-acting medication that should be taken only for daily activities that require relief from muscle spasticity.

Do not take tizanidine if you are also taking the antidepressant fluvoxamine (Luvox), or the antibiotic ciprofloxacin (Cipro).

Do not use tizanidine at a time when muscle tone is needed to assure safe balance and movement for certain activities. In some situations, it may endanger your physical safety to be in a state of reduced muscle tone.

Switching between tizanidine tablets and capsules, or changing the way you take it with regard to eating, can cause an increase in side effects or a decrease in therapeutic effect. Follow your doctor's instructions carefully. After making any changes in how you take tizanidine, contact your doctor if you notice any change in how well the medicine works or if it causes increased side effects.

Do not take more than three doses (36 mg) of tizanidine in a 24-hour period. Too much of this medication can damage your liver.

Cold or allergy medicine, narcotic pain medicine, sleeping pills, other muscle relaxers, and medicine for seizures, depression or anxiety can add to sleepiness caused by tizanidine. Tell your doctor if you need to use any of these other medicines together with tizanidine.

Avoid drinking alcohol. It can increase some of the side effects of tizanidine.

Patient Detailed How Take

What should I discuss with my healthcare provider before taking tizanidine (Zanaflex)?

 

Do not use this medication if you are allergic to tizanidine, or if you are also taking the antidepressant fluvoxamine (Luvox), or the antibiotic ciprofloxacin (Cipro).

Before using tizanidine, tell your doctor if you are allergic to any drugs, or if you have:

  • liver disease;
  • kidney disease;
  • high or low blood pressure; or
  • a history of "Long QT syndrome."

If you have any of these conditions, you may not be able to use tizanidine, or you may need a dosage adjustment or special tests during treatment.

FDA pregnancy category C. This medication may be harmful to an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant during treatment.

It is not known whether tizanidine passes into breast milk or if it could harm a nursing baby. Do not use this medication without telling your doctor if you are breast-feeding a baby.

In older adults, tizanidine may take much longer to clear from the body. Follow your doctor's instructions about your specific dosage and medication schedule.

How should I take tizanidine (Zanaflex)?

 

Take this medication exactly as it was prescribed for you. Do not take the medication in larger amounts, or take it for longer than recommended by your doctor. Follow the directions on your prescription label.

Your doctor may occasionally change your dose to make sure you get the best results from this medication.

Take this medication with a full glass of water.

Tizanidine is a short-acting medication, and its effects will be most noticeable between 1 and 6 hours after you take it. This medication should be taken only for daily activities that require relief from muscle spasticity.

In most cases, you may take up to three doses in one day if needed. Allow 6 to 8 hours to pass between doses.

Carefully follow your doctor's instructions about taking this medication with or without food. Taking tizanidine tablets with food can increase the levels of tizanidine in your blood stream, but taking tizanidine capsules with food can decrease the levels.

Switching between tizanidine tablets and capsules, or changing the way you take it with regard to eating, can cause an increase in side effects or a decrease in therapeutic effect. Follow your doctor's instructions carefully. After making any changes in how you take tizanidine, contact your doctor if you notice any change in how well the medicine works or if it causes increased side effects.

Do not take more than three doses (36 mg) in a 24-hour period. Too much of this medication can damage your liver.

To be sure this medication is not causing harmful effects, your liver function will need to be tested on a regular basis. Do not miss any scheduled visits to your doctor.

You may have withdrawal symptoms such as dizziness, fast heart rate, tremors, anxiety, and increased spasticity when you stop using tizanidine after using it over a long period of time. Do not stop using this medication suddenly without first talking to your doctor. You may need to use less and less before you stop the medication completely.

Store tizanidine at room temperature away from moisture and heat.

Patient Detailed Avoid Taking

What happens if I miss a dose (Zanaflex)?

 

Take the missed dose as soon as you remember. If it is almost time for your next dose, skip the missed dose and take the medicine at your next regularly scheduled time. Do not take extra medicine to make up the missed dose.

What happens if I overdose (Zanaflex)?

 

Seek emergency medical attention if you think you have used too much of this medicine.

Overdose symptoms may include drowsiness, confusion, slow heart rate, shallow breathing, feeling light-headed, fainting, or coma.

What should I avoid while taking tizanidine (Zanaflex)?

 

Tizanidine can cause side effects that may impair your thinking or reactions. Be careful if you drive or do anything that requires you to be awake and alert. Dizziness is most likely to occur when you rise from a sitting or lying position. Get up slowly to prevent dizziness and a possible fall.

Do not use tizanidine at a time when muscle tone is needed to assure safe balance and movement for certain activities. In some situations, it may endanger your physical safety to be in a state of reduced muscle tone.

Cold or allergy medicine, narcotic pain medicine, sleeping pills, other muscle relaxers, and medicine for seizures, depression or anxiety can add to sleepiness caused by tizanidine. Tell your doctor if you need to use any of these other medicines together with tizanidine.

Avoid drinking alcohol. It can increase some of the side effects of tizanidine.

What other drugs will affect tizanidine (Zanaflex)?

 

Before taking tizanidine, tell your doctor if you are using any of the following drugs:

  • acyclovir (Zovirax);
  • cimetidine (Tagamet);
  • famotidine (Pepcid);
  • ticlopidine (Ticlid),
  • zileuton (Zyflo);
  • birth control pills;
  • antibiotics such as enoxacin (Penetrex), gatifloxacin (Tequin), levofloxacin (Levaquin), lomefloxacin (Maxaquin), moxifloxacin (Avelox), ofloxacin (Floxin), sparfloxacin (Zagam), trovafloxacin (Trovan), or norfloxacin (Noroxin);
  • blood pressure medications such as clonidine (Catapres), guanabenz (Wytensin), guanfacine (Tenex), or methyldopa (Aldomet); or
  • heart rhythm medications such as amiodarone (Cordarone, Pacerone), mexiletine (Mexitil), propafenone (Rhythmol), and verapamil (Calan, Covera, Isoptin).

This list is not complete and there may be other drugs that can interact with tizanidine. Tell your doctor about all the prescription and over-the-counter medications you use. This includes vitamins, minerals, herbal products, and drugs prescribed by other doctors. Do not start using a new medication without telling your doctor.

Where can I get more information?

 

Your pharmacist can provide more information about tizanidine.


Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.

Every effort has been made to ensure that the information provided by Cerner Multum, Inc. ('Multum') is accurate, up-to-date, and complete, but no guarantee is made to that effect. Drug information contained herein may be time sensitive. Multum information has been compiled for use by healthcare practitioners and consumers in the United States and therefore Multum does not warrant that uses outside of the United States are appropriate, unless specifically indicated otherwise. Multum's drug information does not endorse drugs, diagnose patients or recommend therapy. Multum's drug information is an informational resource designed to assist licensed healthcare practitioners in caring for their patients and/or to serve consumers viewing this service as a supplement to, and not a substitute for, the expertise, skill, knowledge and judgment of healthcare practitioners. The absence of a warning for a given drug or drug combination in no way should be construed to indicate that the drug or drug combination is safe, effective or appropriate for any given patient. Multum does not assume any responsibility for any aspect of healthcare administered with the aid of information Multum provides. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the drugs you are taking, check with your doctor, nurse or pharmacist.

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