Tizanidine: Package Insert and Label Information

TIZANIDINE- tizanidine hydrochloride tablet
AvKARE

1 INDICATIONS AND USAGE

Tizanidine Tablets, USP 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, USP should be reserved for those daily activities and times when relief of spasticity is most important [see Dosage and Administration (2.1)].

2 DOSAGE AND ADMINISTRATION

2.1 Dosing Information

Tizanidine Tablets, USP 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, USP 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 Tablets, USP 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 Tablets, USP 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 Tablets, USP 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)].

3 DOSAGE FORMS AND STRENGTHS

Tizanidine Tablets, USP 2 mg are white to off-white, round, flat beveled, uncoated tablets debossed with product code “502” on one side, and bisecting score on the other.

Tizanidine Tablets, USP 4 mg are white to off-white, round, flat beveled, uncoated tablets debossed with product code “503” on one side, and quadrisecting score on the other.

4 CONTRAINDICATIONS

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

5 WARNINGS AND PRECAUTIONS

5.1 Hypotension

Tizanidine is an α ₂ -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 Tablets, USP is used in patients receiving concurrent antihypertensive therapy. It is not recommended thatTizanidine Tablets, USP be used with other α ₂ -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 Tablets, USP. Therefore, concomitant use of Tizanidine Tablets, USP 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 Tablets, USP may cause hepatocellular liver injury. Tizanidine Tablets, USP 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 Tablets, USP 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 Tablets, USP with alcohol and other CNS depressants (e.g., benzodiazepines, opioids, tricyclic antidepressants) may be additive. Monitor patients who take Tizanidine Tablets, USP with another CNS depressant for symptoms of excess sedation. [ see Drug Interactions (7.5, 7.6 )]

5.4 Hallucinosis/Psychotic-Like Symptoms

Tizanidine Tablets, USP 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 Tablets, USP in patients who develop hallucinations.

5.5 Interaction with CYP1A2 Inhibitors

Because of potential drug interactions, Tizanidine Tablets, USP 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 Tablets, USP 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 Tablets, USP 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 Tablets, USP 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 Tablets, USP 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 Tablets, USP 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)]

6 ADVERSE REACTIONS

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 Tablets, USP where the frequency in the Tizanidine Tablets, USP 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, USP Incidence is Greater than Placebo

Event	Placebo N = 261 %	Tizanidine Tablets, USP 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 (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

Event	Placebo N = 48 %	Tizanidine Tablets, USP, 8 mg, N = 45 %	Tizanidine Tablets, USP, 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)