TIZANIDINE

Tizanidine hydrochloride USP, is a central α 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 C 9 H 8 ClN 5 S.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. structure

Tizanidine tablets are indicated for the treatment of spasticity in adults. Tizanidine tablet is a central alpha-2-adrenergic agonist indicated for the treatment of spasticity. ( 1 )

Monitoring of aminotransferase levels is recommended at baseline and 1month after maximum dose is achieved. (2.1) Recommended starting dose: 2 mg by mouth every 6 to 8 hours, as needed, up to a maximum of 3 doses in 24 hours (2.2) Dosage can be increased by 2 mg to 4 mg per dose every1 to 4 days; maximum total daily dosage is 36 mg (2.2) 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. Consistent administration with respect to food is recommended. If substitution between dosage forms is necessary, take into consideration these pharmacokinetic differences. ( 2.2 , 2.6, 12.3) Patients with renal impairment (creatinine clearance <25 mL/min) or hepatic impairment: use lower individual doses during titration. If higher doses are required, individual doses rather than dosing frequency should be increased. (2.3 , 2.4 ) To discontinue tizanidine tablets, decrease dose slowly to minimize the risk of withdrawal adverse reactions (2.5) 2.1 Recommended Evaluation and Testing Before and After Initiating Tizanidine tablets 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 dosebased 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 tablets between the fed or fasted state [see Clinical Pharmacology (12.3) ] . Tizanidine tablets 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 tablets 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 lowerindividual 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 Tablets When discontinuing tizanidine tablets, particularly in patients who have been receiving high doses for long periods or who may be on concomitant treatment with narcotics, decreasethe 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 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 hydrochloride 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 tablets. Symptoms have included anaphylaxis and angioedema [see Warnings and Precautions (5.5) ]. Concomitant use with strong CYP1A2 inhibitors ( 4 , 7.1) Patients with a history of hypersensitivity to tizanidine or the ingredientsin tizanidine tablets (4, 5.5)

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 10% of patients taking tizanidine and greater than in patients taking placebo) were dry mouth, somnolence, asthenia, and dizziness. ( 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. 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 patientswere 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 hydrochloride where the frequency in the tizanidine hydrochloride group was greater than the placebo group. Table 1: Multiple Dose, Placebo-Controlled Studies—Adverse Reactions Reported in >2% of Patients Treated with Tizanidine Tablets and Incidence Greater than Placebo Adverse Reaction 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 Liver test abnormality 2 6 Constipation 1 4 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 Adverse Reaction 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 Postmarketing Experience The following adverse reactions have been identified during post approval use of tizanidine hydrochloride. 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 [seeWarnings and Precautions (5.5)], exfoliative dermatitis, rash

Moderate or weak CYP1A2 inhibitors: avoid concomitant use; may cause hypotension, bradycardia, or excessive drowsiness; if concomitant use is necessary and adverse reactions occur, reduce tizanidine hydrochloride dosage or discontinue. ( 7.2 , 12.3 ) 7.1 Strong CYP1A2 Inhibitors Concomitant use of tizanidine hydrochloride 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 Inhibitors Concomitant use of tizanidine hydrochloride 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 hydrochloride dosage or discontinue tizanidine hydrochloride therapy. [see Clinical Pharmacology (12.3) ]. 7.3 Oral Contraceptives Concomitant use of tizanidine hydrochloride 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 hydrochloride therapy [see Clinical Pharmacology (12.3) ]. 7.4 Alcohol and Other CNS Depressants Alcohol increases the exposure of tizanidine after administration of tizanidine hydrochloride. This was associated with an increase in adverse reactions of tizanidine hydrochloride. Concomitant use of tizanidine hydrochloride with CNS depressants (e.g., alcohol, benzodiazepines, opioids, tricyclic antidepressants) may cause additive CNS depressant effects, including sedation. Monitor patients who take tizanidine hydrochloride 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 with antihypertensive medications may cause additive hypotensive effects [see Warnings and Precautions (5.1) ] . Monitor patients who take Tizanidine with antihypertensive medications for hypotension.