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Tizanidine
GenericID: 35356066214
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TL;DR — Quick Summary
Key facts from the full medication guide below
🩺What it's for
Tizanidine tablet is a central alpha-2-adrenergic agonist indicated for the management of spasticity. Because of the short duration of therapeutic effect, treatment with tizanidine tablets should be reserved for those daily activities and times when relief of spasticity is most important [see Dosage and Administration (2.1)]. Tizanidine tablet is a central alpha-2-adrenergic agonist indicated for the management of spasticity.
💊How to take it
Recommended starting dose: 2 mg; dose can be repeated at 6 to 8 hourintervals, up to a maximum of 3 doses in 24 hours (2.1) Dosage can be increased by 2 mg to 4 mg per dose, with 1 to 4 daysbetween increases; total daily dose should not exceed 36 mg (2.1) Tizanidine pharmacokinetics differs between tablets and capsules, andwhen taken with or without food.
ℹ️Common side effects
The following adverse reactions are described elsewhere in other sections of the prescribing information: Hypotension [see Warnings and Precautions (5.1)] Liver Injury [see Warnings and Precautions (5.2)] Sedation [see Warnings and Precautions (5.3)] Hallucinosis/Psychotic-Like Symptoms [see Warnings and Precautions (5.4)] Hypersensitivity Reactions [see Warnings and Precautions (5.6)] The most common adverse reactions (greater than 2% of 264 patients taking tizanidine and greater than in…
⚠️Serious risks
Hypotension: monitor for signs and symptoms of hypotension, in particular in patients receiving concurrent antihypertensives; tizanidine hydrochloride should not be used with other 2-adrenergic agonists (5.1, 7.7) Risk of liver injury: monitor ALTs; discontinue tizanidine hydrochloride if liver injury occurs (5.2) Sedation: tizanidine hydrochloride may interfere with everyday activities; sedative effects of tizanidine hydrochloride, alcohol, and other CNS depressants are additive (5.3, 7.5,…
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Recommended starting dose: 2 mg; dose can be repeated at 6 to 8 hourintervals, up to a maximum of 3 doses in 24 hours (2.1) Dosage can be increased by 2 mg to 4 mg per dose, with 1 to 4 daysbetween increases; total daily dose should not exceed 36 mg (2.1) Tizanidine pharmacokinetics differs between tablets and capsules, andwhen taken with or without food. These differences could result in achange in tolerability and control of symptoms (2.1, 12.3) To discontinue tizanidine tablet, decrease dose slowly to minimize the risk of withdrawal and rebound hypertension, tachycardia, and hypertonia (2.2)
Tizanidine Tablets USP, 2 mgare white to off white, oval, flat, beveled edged tablets debossed with R179 on one side and bisecting score on other side. The tablets are available in bottles of 30, 150, 300 and 1000. 353560662-14 35356-662-30 35356-662-60 35356-662-90 35356-662-18 Tizanidine Tablets USP, 4 mg are white to off white, oval, flat, beveled edged tablets debossed with R180 on one side and quadrisecting score on other side. The tablets are available in bottles of 30, 150, 300 and 1000. 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.
Tablets Tizanidine Tablets USP, 2 mgare white to off white, oval, flat, beveled edged tablets debossed with R179 on one side and bisecting score on other side. Tizanidine Tablets USP, 4 mg are white to off white, oval, flat, beveled edged tablets debossed with R180 on one side and quadrisecting score on other side. Tablets 2 mg & 4 mg (3)
Tizanidine hydrochloride is contraindicated in patients taking potent inhibitors of CYP1A2, such as fluvoxamine or ciprofloxacin [see Drug Interactions ( 7.1, 7.2 )]. Concomitant use with potent inhibitors of CYP1A2, such as fluvoxamine or ciprofloxacin (4, 5.5, 7.1, 7.2)
Hypotension: monitor for signs and symptoms of hypotension, in particular in patients receiving concurrent antihypertensives; tizanidine hydrochloride should not be used with other 2-adrenergic agonists (5.1, 7.7) Risk of liver injury: monitor ALTs; discontinue tizanidine hydrochloride if liver injury occurs (5.2) Sedation: tizanidine hydrochloride may interfere with everyday activities; sedative effects of tizanidine hydrochloride, alcohol, and other CNS depressants are additive (5.3, 7.5, 7.6) Hallucinations: consider discontinuation of tizanidine hydrochloride (5.4) Less potent inhibitors of CYP1A2: may cause hypotension, bradycardia, or excessive drowsiness, use caution if tizanidine hydrochloride is used with less potent inhibitors of CYP1A2, e.g., zileuton, other fluoroquinolones, antiarrythmics , cimetidine, famotidine, oral contraceptives, acyclovir, and ticlopidine (5.5, 7.3,12.3) Renal impairment (creatinine clearance < 25 mL/min): use tizanidine hydrochloride with caution, and monitor closely for dry mouth, somnolence, asthenia and dizziness as indicators of potential overdose (5.7)
The following adverse reactions are described elsewhere in other sections of the prescribing information: Hypotension [see Warnings and Precautions (5.1)] Liver Injury [see Warnings and Precautions (5.2)] Sedation [see Warnings and Precautions (5.3)] Hallucinosis/Psychotic-Like Symptoms [see Warnings and Precautions (5.4)] Hypersensitivity Reactions [see Warnings and Precautions (5.6)] The most common adverse reactions (greater than 2% of 264 patients taking tizanidine and greater than in placebo-treated patients in three multiple dose, placebo-controlled studies) were dry mouth, somnolence, asthenia, dizziness, urinary tract infection, constipation, liver function tests abnormal, vomiting,speech disorder, amblyopia, urinary frequency, flu syndrome, SGPT/ALT increased, dyskinesia, nervousness, pharyngitis, and rhinitis (6.1) To report SUSPECTED ADVERSE REACTIONS, contact Dr. Reddy s Laboratories Inc., at 1-888-375-3784 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.
Pregnancy: Based on animal data, may cause fetal harm (8.1) Geriatric use: tizanidine hydrochloride should be used with caution in elderly patients because clearance is decreased four-fold (8.5)
Pregnancy Category C Tizanidine hydrochloride has not been studied in pregnant women. Tizanidine hydrochloride 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.
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 tizanidine hydrochloride is administered to a nursing woman.
Safety and effectiveness in pediatric patients have not been established.
Tizanidine hydrochloride 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 tizanidine hydrochloride did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently than younger subjects. Cross-study comparison of pharmacokinetic data following single dose administration of 6 mg tizanidine hydrochloride 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 tizanidine hydrochloride.
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 (2.3), Warnings and Precautions (5.2), and Clinical Pharmacology (12.3)].
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.
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 included hypertension, 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 minimizethe risk of withdrawal symptoms [see Dosage and Administration (2.2)]. 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, body twitching, and aversive behavior toward the observer) were not reversed by naloxone administration.
A review of the safety surveillance database revealed cases of intentional and accidental tizanidine hydrochloride 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 often bradycardia 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.
Tizanidine hydrochloride USP, is a central 2-adrenergic agonist. Tizanidine hydrochloride USP is almost white to slightly yellow crystalline powder, which is slightly soluble in water and methanol. Its chemical name is 5-chloro-4-(2-imidazolin-2-ylamino)-2,1,3-benzothiodiazole monohydrochloride. Tizanidine s molecular formula is C9H8ClN5S.HCl, its molecular weight is 290.2 and its structural formula is: Tizanidine tablets USP, are supplied as 2 mg and 4 mg tablets for oral administration. Tizanidine tablets USP, contain the active ingredient, tizanidine hydrochloride USP (2.288 mg equivalent to 2 mg tizanidine base and 4.576 mg equivalent to 4 mg tizanidine base), and the inactive ingredients, anhydrous lactose, microcrystalline cellulose, colloidal silicon dioxide and stearic acid.
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.
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 Tizanidine Capsules and Tizanidine Tablets Tizanidine capsules and tizanidine 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 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% to 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 Tizanidine Tablets and Capsules (2 4 mg) Under Fasted and Fed Conditions Metabolism and Excretion Tizanidine has linear pharmacokinetics over the doses studied in clinical development (1 to 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 tizanidine hydrochloride showed that younger subjects cleared the drug four times faster than the elderly subjects. Tizanidine hydrochloride has not been evaluated in children. [see Use in Specific Populations (8.4, 8.5)] 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. Tizanidine hydrochloride is not recommended in this patient population [see Use in Specific Populations (8.7)] 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. Tizanidine hydrochloride should be used with caution in renally impaired patients [see Warnings and Precautions (5.7) and Use in Specific Populations (8.6)]. 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 tizanidine hydrochloride 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 tizanidine hydrochloride 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 tizanidine hydrochloride 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 tizanidine hydrochloride was studied in 10 healthy subjects. The Cmax and AUC of tizanidine increased by 7-fold and 10-fold, respectively. [see Contraindications (4)] 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 (5.5)]. 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 tizanidine hydrochloride. Retrospective analysis of population pharmacokinetic data following single and multiple dose administration of 4 mg tizanidine hydrochloride, 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 (5.5)]. 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.
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).
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 tizanidine hydrochloride. 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 tizanidine hydrochloride 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 tizanidine hydrochloride 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) Seven-Week Study in Patients with Spinal Cord Injury with SpasticityIn a 7-week study (Study 2), 118 patients with spasticity secondary to spinal cord injury were randomized to either placebo or tizanidine hydrochloride. 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 tizanidine hydrochloride 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 tizanidine hydrochloride 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 to 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)
Serious Drug Interactions Advise patients they should not take tizanidine hydrochloride 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 tizanidine hydrochloride and other medicines. Tizanidine hydrochloride Dosing Tell patients to take tizanidine hydrochloride 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 tizanidine hydrochloride 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 tizanidine hydrochloride, because rebound hypertension and tachycardia may occur. Effects of Tizanidine Hydrochloride 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 tizanidine hydrochloride 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 tizanidine hydrochloride 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 Tizanidine hydrochloride decreases spasticity and caution should be used. Rx Only Manufactured by Dr. Reddy s Laboratories Limited Bachupally - 500 090 INDIA Revised: 0617 or Manufactured by: Dr. Reddy s Laboratories Limited Srikakulam - 532 409 INDIA Revised: 0617
