Tizanidine HCl

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Overview

What is Tizanidine HCl?

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: molecular structure

Tizanidine tablets are supplied as 2 mg and 4 mg tablets for oral administration. Tizanidine tablets contain the active ingredient, tizanidine hydrochloride (2.288 mg equivalent to 2 mg tizanidine base and 4.576 mg equivalent to 4 mg tizanidine base), and the inactive ingredients, colloidal silicon dioxide, stearic acid, microcrystalline cellulose and anhydrous lactose.

Please review the manufacturer's complete drug information available from the FDA at www.fda.gov Permanent Link: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=a3fa9c69-4baf-44f5-bac4-a19c34b0e1cb

What does Tizanidine HCl look like?

What are the available doses of Tizanidine HCl?

Tablets

Tizanidine tablets 2 mg are white to off-white, round, flat, bevel edged uncoated tablets debossed with "U" and "168" on one side and bisecting score on other.

Tizanidine tablets 4 mg are white to off-white, round, flat, bevel edged uncoated tablets debossed with "U" and "169" on one side and quadrisecting score on other.

Please review the manufacturer's complete drug information available from the FDA at www.fda.gov Permanent Link: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=a3fa9c69-4baf-44f5-bac4-a19c34b0e1cb

What should I talk to my health care provider before I take Tizanidine HCl?

8.1 Pregnancy

Pregnancy Category C

Tizanidine has not been studied in pregnant women. Tizanidine 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.

8.3 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 tizanidine is administered to a nursing woman.

8.4 Pediatric use

Safety and effectiveness in pediatric patients have not been established.

8.5 Geriatric use

Tizanidine 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 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 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.

8.6 Impaired Renal Function

Tizanidine 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 (2.2), Warnings and Precautions (5.7) and Clinical Pharmacology (12.3)]

8.7 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 (2.3), Warnings and Precautions (5.2), and Clinical Pharmacology (12.3)].

Please review the manufacturer's complete drug information available from the FDA at www.fda.gov Permanent Link: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=a3fa9c69-4baf-44f5-bac4-a19c34b0e1cb

How should I use Tizanidine HCl?

Tizanidine is a central alpha-2-adrenergic agonist indicated for the management of spasticity. Because of the short duration of therapeutic effect, treatment with tizanidine should be reserved for those daily activities and times when relief of spasticity is most important [see Dosage and Administration (2.1)].

Please review the manufacturer's complete drug information available from the FDA at www.fda.gov Permanent Link: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=a3fa9c69-4baf-44f5-bac4-a19c34b0e1cb

2.1 Dosing Information

Tizanidine 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. Tizanidine Capsules and tizanidine 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 (12.3)].

The recommended starting dose is 2 mg. Because the effect of tizanidine 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.

2.2 Dosing in Patients with Renal Impairment

Tizanidine 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 (5.7)].

2.3 Dosing in Patients with Hepatic Impairment

Tizanidine 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 (8.7)]

2.4 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 [see Drug Abuse and Dependence (9.3)].

What interacts with Tizanidine HCl?

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What are the warnings of Tizanidine HCl?

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What are the precautions of Tizanidine HCl?

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What are the side effects of Tizanidine HCl?

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What should I look out for while using Tizanidine HCl?

Tizanidine is contraindicated in patients taking potent inhibitors of CYP1A2, such as fluvoxamine or ciprofloxacin [see Drug Interactions (7.1, 7.2)].

Please review the manufacturer's complete drug information available from the FDA at www.fda.gov Permanent Link: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=a3fa9c69-4baf-44f5-bac4-a19c34b0e1cb

What might happen if I take too much Tizanidine HCl?

A review of the safety surveillance database revealed cases of intentional and accidental tizanidine 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.

Please review the manufacturer's complete drug information available from the FDA at www.fda.gov Permanent Link: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=a3fa9c69-4baf-44f5-bac4-a19c34b0e1cb

How should I store and handle Tizanidine HCl?

Storage: Store Naftifine Hydrochloride Cream USP, 2% at ° [see USP Controlled Room Temperature].16.2 Tizanidine TabletsTizanidine (tizanidine hydrochloride) tablets USP are available as white to off-white, round, flat, bevel edged uncoated tablets containing 2 mg or 4 mg of tizanidine.Tizanidine tablets USP 2 mg are debossed with "U" and "168" on one side and bisecting score on other side.Bottles of 150: NDC 29300-168-15Bottles of 500: NDC 29300-168-05Bottles of 1000: NDC 29300-168-10Tizanidine tablets USP 4 mg are debossed with "U" and "169" on one side and quadrisecting score on other side.Bottles of 150: NDC 29300-169-15Bottles of 300: NDC 29300-169-03Bottles of 500: NDC 29300-169-05Bottles of 1000: NDC 29300-169-10Store at 20° to 25°C (68° to 77°F) [see USP Controlled Room Temperature].Dispense in tight, light-resistant container [see USP]. 16.2 Tizanidine TabletsTizanidine (tizanidine hydrochloride) tablets USP are available as white to off-white, round, flat, bevel edged uncoated tablets containing 2 mg or 4 mg of tizanidine.Tizanidine tablets USP 2 mg are debossed with "U" and "168" on one side and bisecting score on other side.Bottles of 150: NDC 29300-168-15Bottles of 500: NDC 29300-168-05Bottles of 1000: NDC 29300-168-10Tizanidine tablets USP 4 mg are debossed with "U" and "169" on one side and quadrisecting score on other side.Bottles of 150: NDC 29300-169-15Bottles of 300: NDC 29300-169-03Bottles of 500: NDC 29300-169-05Bottles of 1000: NDC 29300-169-10Store at 20° to 25°C (68° to 77°F) [see USP Controlled Room Temperature].Dispense in tight, light-resistant container [see USP]. 16.2 Tizanidine TabletsTizanidine (tizanidine hydrochloride) tablets USP are available as white to off-white, round, flat, bevel edged uncoated tablets containing 2 mg or 4 mg of tizanidine.Tizanidine tablets USP 2 mg are debossed with "U" and "168" on one side and bisecting score on other side.Bottles of 150: NDC 29300-168-15Bottles of 500: NDC 29300-168-05Bottles of 1000: NDC 29300-168-10Tizanidine tablets USP 4 mg are debossed with "U" and "169" on one side and quadrisecting score on other side.Bottles of 150: NDC 29300-169-15Bottles of 300: NDC 29300-169-03Bottles of 500: NDC 29300-169-05Bottles of 1000: NDC 29300-169-10Store at 20° to 25°C (68° to 77°F) [see USP Controlled Room Temperature].Dispense in tight, light-resistant container [see USP]. 16.2 Tizanidine TabletsTizanidine (tizanidine hydrochloride) tablets USP are available as white to off-white, round, flat, bevel edged uncoated tablets containing 2 mg or 4 mg of tizanidine.Tizanidine tablets USP 2 mg are debossed with "U" and "168" on one side and bisecting score on other side.Bottles of 150: NDC 29300-168-15Bottles of 500: NDC 29300-168-05Bottles of 1000: NDC 29300-168-10Tizanidine tablets USP 4 mg are debossed with "U" and "169" on one side and quadrisecting score on other side.Bottles of 150: NDC 29300-169-15Bottles of 300: NDC 29300-169-03Bottles of 500: NDC 29300-169-05Bottles of 1000: NDC 29300-169-10Store at 20° to 25°C (68° to 77°F) [see USP Controlled Room Temperature].Dispense in tight, light-resistant container [see USP]. 16.2 Tizanidine TabletsTizanidine (tizanidine hydrochloride) tablets USP are available as white to off-white, round, flat, bevel edged uncoated tablets containing 2 mg or 4 mg of tizanidine.Tizanidine tablets USP 2 mg are debossed with "U" and "168" on one side and bisecting score on other side.Bottles of 150: NDC 29300-168-15Bottles of 500: NDC 29300-168-05Bottles of 1000: NDC 29300-168-10Tizanidine tablets USP 4 mg are debossed with "U" and "169" on one side and quadrisecting score on other side.Bottles of 150: NDC 29300-169-15Bottles of 300: NDC 29300-169-03Bottles of 500: NDC 29300-169-05Bottles of 1000: NDC 29300-169-10Store at 20° to 25°C (68° to 77°F) [see USP Controlled Room Temperature].Dispense in tight, light-resistant container [see USP]. 16.2 Tizanidine TabletsTizanidine (tizanidine hydrochloride) tablets USP are available as white to off-white, round, flat, bevel edged uncoated tablets containing 2 mg or 4 mg of tizanidine.Tizanidine tablets USP 2 mg are debossed with "U" and "168" on one side and bisecting score on other side.Bottles of 150: NDC 29300-168-15Bottles of 500: NDC 29300-168-05Bottles of 1000: NDC 29300-168-10Tizanidine tablets USP 4 mg are debossed with "U" and "169" on one side and quadrisecting score on other side.Bottles of 150: NDC 29300-169-15Bottles of 300: NDC 29300-169-03Bottles of 500: NDC 29300-169-05Bottles of 1000: NDC 29300-169-10Store at 20° to 25°C (68° to 77°F) [see USP Controlled Room Temperature].Dispense in tight, light-resistant container [see USP]. 16.2 Tizanidine TabletsTizanidine (tizanidine hydrochloride) tablets USP are available as white to off-white, round, flat, bevel edged uncoated tablets containing 2 mg or 4 mg of tizanidine.Tizanidine tablets USP 2 mg are debossed with "U" and "168" on one side and bisecting score on other side.Bottles of 150: NDC 29300-168-15Bottles of 500: NDC 29300-168-05Bottles of 1000: NDC 29300-168-10Tizanidine tablets USP 4 mg are debossed with "U" and "169" on one side and quadrisecting score on other side.Bottles of 150: NDC 29300-169-15Bottles of 300: NDC 29300-169-03Bottles of 500: NDC 29300-169-05Bottles of 1000: NDC 29300-169-10Store at 20° to 25°C (68° to 77°F) [see USP Controlled Room Temperature].Dispense in tight, light-resistant container [see USP]. 16.2 Tizanidine TabletsTizanidine (tizanidine hydrochloride) tablets USP are available as white to off-white, round, flat, bevel edged uncoated tablets containing 2 mg or 4 mg of tizanidine.Tizanidine tablets USP 2 mg are debossed with "U" and "168" on one side and bisecting score on other side.Bottles of 150: NDC 29300-168-15Bottles of 500: NDC 29300-168-05Bottles of 1000: NDC 29300-168-10Tizanidine tablets USP 4 mg are debossed with "U" and "169" on one side and quadrisecting score on other side.Bottles of 150: NDC 29300-169-15Bottles of 300: NDC 29300-169-03Bottles of 500: NDC 29300-169-05Bottles of 1000: NDC 29300-169-10Store at 20° to 25°C (68° to 77°F) [see USP Controlled Room Temperature].Dispense in tight, light-resistant container [see USP]. 16.2 Tizanidine TabletsTizanidine (tizanidine hydrochloride) tablets USP are available as white to off-white, round, flat, bevel edged uncoated tablets containing 2 mg or 4 mg of tizanidine.Tizanidine tablets USP 2 mg are debossed with "U" and "168" on one side and bisecting score on other side.Bottles of 150: NDC 29300-168-15Bottles of 500: NDC 29300-168-05Bottles of 1000: NDC 29300-168-10Tizanidine tablets USP 4 mg are debossed with "U" and "169" on one side and quadrisecting score on other side.Bottles of 150: NDC 29300-169-15Bottles of 300: NDC 29300-169-03Bottles of 500: NDC 29300-169-05Bottles of 1000: NDC 29300-169-10Store at 20° to 25°C (68° to 77°F) [see USP Controlled Room Temperature].Dispense in tight, light-resistant container [see USP]. 16.2 Tizanidine TabletsTizanidine (tizanidine hydrochloride) tablets USP are available as white to off-white, round, flat, bevel edged uncoated tablets containing 2 mg or 4 mg of tizanidine.Tizanidine tablets USP 2 mg are debossed with "U" and "168" on one side and bisecting score on other side.Bottles of 150: NDC 29300-168-15Bottles of 500: NDC 29300-168-05Bottles of 1000: NDC 29300-168-10Tizanidine tablets USP 4 mg are debossed with "U" and "169" on one side and quadrisecting score on other side.Bottles of 150: NDC 29300-169-15Bottles of 300: NDC 29300-169-03Bottles of 500: NDC 29300-169-05Bottles of 1000: NDC 29300-169-10Store at 20° to 25°C (68° to 77°F) [see USP Controlled Room Temperature].Dispense in tight, light-resistant container [see USP]. 16.2 Tizanidine TabletsTizanidine (tizanidine hydrochloride) tablets USP are available as white to off-white, round, flat, bevel edged uncoated tablets containing 2 mg or 4 mg of tizanidine.Tizanidine tablets USP 2 mg are debossed with "U" and "168" on one side and bisecting score on other side.Bottles of 150: NDC 29300-168-15Bottles of 500: NDC 29300-168-05Bottles of 1000: NDC 29300-168-10Tizanidine tablets USP 4 mg are debossed with "U" and "169" on one side and quadrisecting score on other side.Bottles of 150: NDC 29300-169-15Bottles of 300: NDC 29300-169-03Bottles of 500: NDC 29300-169-05Bottles of 1000: NDC 29300-169-10Store at 20° to 25°C (68° to 77°F) [see USP Controlled Room Temperature].Dispense in tight, light-resistant container [see USP]. 16.2 Tizanidine TabletsTizanidine (tizanidine hydrochloride) tablets USP are available as white to off-white, round, flat, bevel edged uncoated tablets containing 2 mg or 4 mg of tizanidine.Tizanidine tablets USP 2 mg are debossed with "U" and "168" on one side and bisecting score on other side.Bottles of 150: NDC 29300-168-15Bottles of 500: NDC 29300-168-05Bottles of 1000: NDC 29300-168-10Tizanidine tablets USP 4 mg are debossed with "U" and "169" on one side and quadrisecting score on other side.Bottles of 150: NDC 29300-169-15Bottles of 300: NDC 29300-169-03Bottles of 500: NDC 29300-169-05Bottles of 1000: NDC 29300-169-10Store at 20° to 25°C (68° to 77°F) [see USP Controlled Room Temperature].Dispense in tight, light-resistant container [see USP]. 16.2 Tizanidine TabletsTizanidine (tizanidine hydrochloride) tablets USP are available as white to off-white, round, flat, bevel edged uncoated tablets containing 2 mg or 4 mg of tizanidine.Tizanidine tablets USP 2 mg are debossed with "U" and "168" on one side and bisecting score on other side.Bottles of 150: NDC 29300-168-15Bottles of 500: NDC 29300-168-05Bottles of 1000: NDC 29300-168-10Tizanidine tablets USP 4 mg are debossed with "U" and "169" on one side and quadrisecting score on other side.Bottles of 150: NDC 29300-169-15Bottles of 300: NDC 29300-169-03Bottles of 500: NDC 29300-169-05Bottles of 1000: NDC 29300-169-10Store at 20° to 25°C (68° to 77°F) [see USP Controlled Room Temperature].Dispense in tight, light-resistant container [see USP].

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Clinical Information

Chemical Structure

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Clinical Pharmacology

12.1 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.

12.3 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 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 1.0 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 Tizanidine Tablets and Capsules (2 × 4 mg) Under Fasted and Fed Conditions

Figure-1

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 tizanidine showed that younger subjects cleared the drug four times faster than the elderly subjects. Tizanidine 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 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 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 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 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 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 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. Retrospective analysis of population pharmacokinetic data following single and multiple dose administration of 4 mg tizanidine, 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.

Non-Clinical Toxicology

Tizanidine is contraindicated in patients taking potent inhibitors of CYP1A2, such as fluvoxamine or ciprofloxacin [see Drug Interactions (7.1, 7.2)].

Please review the manufacturer's complete drug information available from the FDA at www.fda.gov Permanent Link: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=a3fa9c69-4baf-44f5-bac4-a19c34b0e1cb

The effects of metoclopramide on gastrointestinal motility are antagonized by anticholinergic drugs and narcotic analgesics. Additive sedative effects can occur when metoclopramide is given with alcohol, sedatives, hypnotics, narcotics, or tranquilizers.

The finding that metoclopramide releases catecholamines in patients with essential hypertension suggests that it should be used cautiously, if at all, in patients receiving monoamine oxidase inhibitors.

Absorption of drugs from the stomach may be diminished (e.g., digoxin) by metoclopramide, whereas the rate and/or extent of absorption of drugs from the small bowel may be increased (e.g., acetaminophen, tetracycline, levodopa, ethanol, cyclosporine).

Gastroparesis (gastric stasis) may be responsible for poor diabetic control in some patients. Exogenously administered insulin may begin to act before food has left the stomach and lead to hypoglycemia. Because the action of metoclopramide will influence the delivery of food to the intestines and thus the rate of absorption, insulin dosage or timing of dosage may require adjustment.

5.1 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 tizanidine is used in patients receiving concurrent antihypertensive therapy. It is not recommended that tizanidine 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 tizanidine. Therefore, concomitant use of tizanidine with fluvoxamine or with ciprofloxacin, potent inhibitors of CYP1A2, is contraindicated [see Contraindications (4) and Drug Interactions (7.1, 7.2)].

5.2 Risk of Liver Injury

Tizanidine may cause hepatocellular liver injury. Tizanidine should be used with caution in patients with any hepatic impairment. Monitoring of aminotransferase levels is recommended for baseline and 1 month after maximum dose is achieved, or if hepatic injury is suspected. [see Dosage and Administration (2.3) and Use in Specific Populations (8.7)]

5.3 Sedation

Tizanidine 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 tizanidine with alcohol and other CNS depressants (e.g., benzodiazepines, opioids, tricyclic antidepressants) may be additive. Monitor patients who take tizanidine with another CNS depressant for symptoms of excess sedation. [see Drug Interactions (7.5, 7.6)]

5.4 Hallucinosis/Psychotic-Like Symptoms

Tizanidine 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 tizanidine in patients who develop hallucinations.

5.5 Interaction with CYP1A2 Inhibitors

Because of potential drug interactions, tizanidine 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 tizanidine 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 tizanidine therapy is clinically evident. In such a case, use with caution. [see Drug Interactions (7.3) and Clinical Pharmacology (12.3)]

5.6 Hypersensitivity Reactions

Tizanidine 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 tizanidine and seek immediate medical care should these signs and symptoms occur. [see Contraindications (4)]

5.7 Increased Risk of Adverse Reactions in Patients with Renal Impairment

Tizanidine 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 (2.2) and Use in Specific Populations (8.6)]

5.8 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). [see Dosage and Administration (2.2)]

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)]

6.1 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 tizanidine where the frequency in the tizanidine 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 Tizanidine Tablets Incidence is Greater than Placebo

*(weakness, fatigue, and/or tiredness) Event Placebo N = 261 % Tizanidine 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 symptom 2 3 Dyskinesia 0 3 Nervousness <1 3 Pharyngitis 1 3 Rhinitis 2 3

In the single dose, placebo-controlled study involving 142 patients with spasticity due to multiple sclerosis (Study 1) [see Clinical Studies (14)], 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

*(weakness, fatigue, and/or tiredness) Event Placebo N = 48 % Tizanidine Tablet,8 mg, N = 45 % Tizanidine 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

6.2 Postmarketing Experience

The following adverse reactions have been identified during post approval use of tizanidine. 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 tizanidine. Based on the information provided regarding these reactions, a causal relationship with tizanidine 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

Please review the manufacturer's complete drug information available from the FDA at www.fda.gov Permanent Link: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=a3fa9c69-4baf-44f5-bac4-a19c34b0e1cb

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Reference

This information is obtained from the National Institute of Health's Standard Packaging Label drug database.
"https://dailymed.nlm.nih.gov/dailymed/"

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Tizanidine HCl

Overview

What is Tizanidine HCl?

What does Tizanidine HCl look like?

What are the available doses of Tizanidine HCl?

What should I talk to my health care provider before I take Tizanidine HCl?

How should I use Tizanidine HCl?

What interacts with Tizanidine HCl?

What are the warnings of Tizanidine HCl?

What are the precautions of Tizanidine HCl?

What are the side effects of Tizanidine HCl?

What should I look out for while using Tizanidine HCl?

What might happen if I take too much Tizanidine HCl?

How should I store and handle Tizanidine HCl?

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