TIZANIDINE HYDROCHLORIDE

Tizanidine hydrochloride capsules contains tizanidine hydrochloride as the active ingredient, which is a centrally acting α 2-adrenergic agonist. Its chemical name is 5-chloro-4-(2-imidazolin-2-yl-amino)-2,1,3-benzothiodiazole monohydrochloride. Its structural formula is C9H8CIN5S•HCl and a molecular weight of 290.17. Its structural formula is:: Tizanidine hydrochloride is almost white to slightly yellow, crystalline powder, which is odorless or with a faint characteristic odor. Tizanidine hydrochloride is slightly soluble in water and methanol; solubility in water decreases as the pH increases. Tizanidine hydrochloride capsules 2 mg, 4 mg and 6 mg, supplied for oral administration, are composed of the active ingredient, tizanidine hydrochloride (2.288 mg equivalent to 2 mg tizanidine base, 4.576mg equivalent to 4 mg tizanidine base, and 6.864 mg equivalent to 6 mg tizanidine base). Each capsule contains the following inactive ingredients: anhydrous lactose, polyvinyl acetate phthalate, stearic acid, and talc. Each capsule shell contains FD&C blue #2, gelatin and titanium dioxide. In addition, the 4 mg capsules shell contains FDA/E172 yellow iron oxide. The capsule printing ink contains black iron oxide, FD&C blue #1, FD&C blue #2, FD&C red #40, and FD&C yellow #10, propylene glycol, and shellac. ChemicalStructure

Tizanidine is indicated for the treatment of spasticity in adults. 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. (1)

Recommended starting dose: 2 mg; dose can be repeated at 6 to 8 hour intervals, 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 days between increases; total daily dose should not exceed 36 mg (2.1) Tizanidine pharmacokinetics differs between tablets and capsules, and when taken with or without food. These differences could result in a change in tolerability and control of symptoms (2.1, 12.3) To discontinue tizanidine, decrease dose slowly to minimize the risk of withdrawal and rebound hypertension, tachycardia, and hypertonia (2.2) 2.1 Recommended Evaluation and Testing Before and After Initiating Tizanidine Monitoring of aminotransferase levels is recommended at baseline and 1 month after maximum dose is achieved[see Warnings and Precautions (5.2)]. 2.2 Recommended Dosage The recommended starting dose is 2 mg by mouth every 6 to 8 hours, as needed, to a maximum of three doses in 24 hours. Dosage can be gradually increased every 1 to 4 days by 2 mg to 4 mg at each dose based on clinical response and tolerability. The maximum total daily dosage is 36 mg. Single doses greater than 16 mg have not been studied. There are pharmacokinetic differences when administering tizanidine between the fed or fasted state [see Clinical Pharmacology (12.3)]. Tizanidine may be taken with or without food; however, consistent administration with respect to food is recommended to reduce variability in tizanidine plasma exposure. 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. 2.3 Recommended Dosage in Patients with Renal Impairment In patients with creatinine clearance < 25 mL/min, use lower individual doses during titration. If higher doses are required, the individual doses rather than dosing frequency should be increased [see Use in Specific Populations (8.6)and Clinical Pharmacology (12.3)]. 2.4 Recommended Dosage in Patients with Hepatic Impairment In patients with hepatic impairment, use lower individual doses during titration. If higher doses are required, individual doses rather than dosing frequency should be increased [see Use in Specific Populations (8.7) and Clinical Pharmacology (12.3)]. 2.5 Discontinuation of Tizanidine Hydrochloride Capsules When discontinuing tizanidine hydrochloride capsules, particularly in patients who have been receiving high doses for long periods or who may be on concomitant treatment with narcotics, decrease the dosage by 2 mg to 4 mg per day to minimize the risk of withdrawal adverse reactions [see Drug Abuse and Dependence (9.3)]. 2.6 Switching Between With/Without Food and Different Tizanidine Dosage Forms There are pharmacokinetic differences when: 1) switching between administration of tizanidine hydrochloride capsules with or without food 2) switching between dosage forms if being administered with food. If these situations occur, monitor patients for therapeutic effect or adverse reactions [see Dosage and Administration (2.2) and Clinical Pharmacology (12.3)].

Tizanidine is contraindicated in patients: taking strong CYP1A2 inhibitors [see Drug Interactions (7.1)]. with a history of hypersensitivity to tizanidine or the ingredients in tizanidine hydrochloride capsules. Symptoms have included anaphylaxis and angioedema [see Warnings and Precautions (5.5)]. Concomitant use with potent inhibitors of CYP1A2, such as fluvoxamine or ciprofloxacin (4, 5.5, 7.1, 7.2)

The following clinically significant 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 (5.5)] • Withdrawal Adverse 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 AvKARE 1-855-361-3993 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch . 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. The safety of tizanidine has been evaluated in three double-blind, randomized, placebo-controlled clinical studies [see Clinical Studies (14)]. 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 period. In all, 264 patients received tizanidine and 261 patients received placebo. Across the three studies approximately 51% of patients were women, and the median dose during the plateau phase ranged from 20 to 28 mg/day. The most common adverse reactions (>10% of patients treated with tizanidine) 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 reactions as mild to moderate and one-quarter of the patients rated the reactions as being severe. These adverse reactions appeared to be dose related. Table 1 lists adverse reactions 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. Table 1: Multiple Dose, Placebo-Controlled Studies—Frequent (>2%) Adverse Reactions Reported for Which Tizanidine Tablets Incidence is Greater than Placebo Placebo Tizanidine Tablet N = 261 N = 264 Event % % 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 * includes 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 Tablet, 8mg, 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 * includes weakness, fatigue, and/or tiredness 6.2 Post-Marketing 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. Cardiac Disorders: Ventricular tachycardia, decreased blood pressure Hepatobiliary Disorders: Hepatotoxicity [see Warnings and Precautions (5.2)], hepatitis Musculoskeletal and Connective Tissue Disorders: arthralgia Nervous System Disorders: Convulsion, paresthesia, tremor, muscle spasms Psychiatric Disorders: Hallucinations [see Warnings and Precautions (5.4)], depression Skin and Subcutaneous Tissue Disorders: Stevens Johnson Syndrome, anaphylactic reaction [see Warnings and Precautions (5.5)], exfoliative dermatitis, rash To report SUSPECTED ADVERSE REACTIONS, contact AvKARE at 1-855-361-3993; email [email protected] or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.

7.1 Strong CYP1A2 Inhibitors Concomitant use of tizanidine with strong cytochrome P450 1A2 (CYP1A2) inhibitors (e.g., fluvoxamine, ciprofloxacin) is contraindicated. Changes in pharmacokinetics of tizanidine when administered with a strong CYP1A2 inhibitor resulted in significantly decreased blood pressure, increased drowsiness, and increased psychomotor impairment [see Contraindications (4) and Clinical Pharmacology (12.3)]. 7.2 Moderate or Weak CYP1A2 Concomitant use of tizanidine with moderate or weak CYP1A2 inhibitors (e.g., zileuton, antiarrhythmics [amiodarone, mexiletine, propafenone, and verapamil], cimetidine, famotidine, oral contraceptives, acyclovir, and ticlopidine) should be avoided. If concomitant use is clinically necessary, and adverse reactions such as hypotension, bradycardia, or excessive drowsiness occur, reduce tizanidine dosage or discontinue tizanidine therapy [see Clinical Pharmacology (12.3)]. 7.3 Oral Contraceptives Concomitant use of tizanidine with oral contraceptives is not recommended. However, if concomitant use is clinically necessary and adverse reactions such as hypotension, bradycardia, or excessive drowsiness occur, reduce or discontinue tizanidine therapy [see Clinical Pharmacology (12.3)]. 7.4 Alcohol and Other CNS Depressants Alcohol increases the exposure of tizanidine after administration of tizanidine. This was associated with an increase in adverse reactions of tizanidine. Concomitant use of tizanidine with CNS depressants (e.g., alcohol, benzodiazepines, opioids, tricyclic antidepressants) may cause additive CNS depressant effects, including sedation. Monitor patients who take tizanidine with another CNS depressant for symptoms of excess sedation [see Clinical Pharmacology (12.3)]. 7.5 α 2 -Adrenergic Agonists Concomitant use of tizanidine with other α2-adrenergic agonists is not recommended because hypotensive effects may be cumulative [see Warnings and Precautions (5.1)]. 7.6 Antihypertensive Medications Concomitant use of tizanidine hydrochloride capsules with antihypertensive medications may cause additive hypotensive effects [see Warnings and Precautions (5.1)]. Monitor patients who take tizanidine with antihypertensive medications for hypotension.