tizanidine hydrochloride

Brand names: tizanidine hydrochloride, Tizanidine Hydrochloride, TIZANIDINE HYDROCHLORIDE, Tizanidine hydrochloride, Zanaflex, Ontralfy

Warnings

5 WARNINGS AND PRECAUTIONS Hypotension: monitor for signs and symptoms of hypotension, in particular in patients receiving concurrent antihypertensives; tizanidine should not be used with other α2-adrenergic agonists (5.1, 7.7) Risk of liver injury: monitor ALTs; discontinue tizanidine if liver injury occurs (5.2) Sedation: Tizanidine may interfere with everyday activities; sedative effects of tizanidine, alcohol, and other central nervous system (CNS) depressants are additive (5.3, 7.4) Hallucinations: consider discontinuation of tizanidine (5.4) 5.1 Hypotension Tizanidine is an α 2 -adrenergic agonist that can produce hypotension [see Adverse Reactions ( 6.1 ) and Drug Interactions ( 7.5 )] . Syncope has been reported in patients treated with tizanidine in the postmarketing setting. The risk of hypotension may be minimized by dose titration; monitoring for signs and symptoms of hypotension prior to dosage increase may minimize the risks associated with hypotension. 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 tizanidine and strong CYP1A2 inhibitors [see Clinical Pharmacology ( 12.3 )]. Therefore, concomitant use of tizanidine with strong CYP1A2 inhibitors is contraindicated [see Contraindications ( 4 ) and Drug Interactions ( 7.1 )] . 5.2 Liver Injury Tizanidine may cause hepatocellular liver injury. Liver function test abnormality and hepatotoxicity have been observed with tizanidine [see Adverse Reactions ( 6.1 , 6.2 )]. Monitoring of aminotransferase levels is recommended at baseline and 1 month after maximum dose is achieved, or if hepatic injury is suspected [see Dosage and Administration ( 2.1 ) 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 of tizanidine, 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 [see Adverse Reactions ( 6.1 )] . The CNS depressant effects of tizanidine with alcohol and other CNS depressants (e.g., benzodiazepines, opioids, tricyclic antidepressants) may be additive [see Drug Interactions ( 7.4 )] . Monitor patients who take tizanidine with another CNS depressant for symptoms of excess sedation. 5.4 Hallucinosis/Psychotic-Like Symptoms Tizanidine use has been associated with hallucinations. Formed, visual hallucinations or delusions were 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. Hallucinations have also been reported with tizanidine use in the postmarketing setting. Consider discontinuing tizanidine in patients who develop hallucinations. 5.5 Hypersensitivity Reactions Tizanidine can cause anaphylaxis. Signs and symptoms of hypersensitivity, including respiratory compromise, urticaria, and angioedema of the throat and tongue, have been reported. Tizanidine is contraindicated in patients with a history of hypersensitivity reactions to tizanidine [see Contraindications ( 4 )]. 5.6 Withdrawal Adverse Reactions Tizanidine can cause withdrawal adverse reactions, which include rebound hypertension, tachycardia, and hypertonia. To minimize the risk of these reactions, particularly in patients who have been receiving high doses of tizanidine (20 to 28 mg daily) for long periods of time (9 weeks or more) or who may be on concomitant treatment with narcotics, the tizanidine dosage should be decreased slowly [see Dosage and Administration ( 2.5 )].

Contraindications

4 CONTRAINDICATIONS Tizanidine Hydrochloride Capsules are 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 strong CYP1A2 inhibitors ( 4 , 7.1 ) Patients with a history of hypersensitivity to tizanidine or the ingredients in tizanidine hydrochloride capsules ( 4 , 5.5 )

Overdose

10 OVERDOSAGE 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, ensure the adequacy of an airway and monitor cardiovascular and respiratory function. Dialysis is not likely to be an efficient method of removing tizanidine from the body [see Description ( 11 )]. In general, symptoms resolve within one to three days following discontinuation of tizanidine and administration of appropriate therapy. Because of 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.

Drug interactions

7 DRUG INTERACTIONS 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 dosage or discontinue. (7.2, 12.3) 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 Inhibitors 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 α2-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.

Uses

1 INDICATIONS AND USAGE Tizanidine Hydrochloride Capsules are indicated for the treatment of spasticity in adults. Tizanidine Hydrochloride Capsules are a central alpha-2-adrenergic agonist indicated for the treatment of spasticity. (1)

Dosage forms & strengths

CAPSULE CAPSULE, GELATIN COATED TABLET POWDER SOLUTION
TIZANIDINE HYDROCHLORIDE 6 mg/1 TIZANIDINE HYDROCHLORIDE 4 mg/1 TIZANIDINE HYDROCHLORIDE 1 g/g TIZANIDINE HYDROCHLORIDE 1 kg/kg TIZANIDINE HYDROCHLORIDE 2 mg/1 TIZANIDINE HYDROCHLORIDE 8 mg/1 TIZANIDINE HYDROCHLORIDE 25 kg/25kg TIZANIDINE HYDROCHLORIDE 2 mg/5mL
2 DOSAGE AND ADMINISTRATION Monitoring of aminotransferase levels is recommended at baseline and 1 month 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 every 1 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, decrease dose slowly to minimize the risk of withdrawal adverse reactions (2.5) 2.1 Recommended Evaluation and Testing Before and After Initiating Tizanidine Hydrochloride Capsules 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 hydrochloride between the fed or fasted state [see Clinical Pharmacology ( 12.3 )]. Tizanidine Hydrochloride Capsules 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 hydrochloride 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: switching between administration of tizanidine hydrochloride capsules with or without food 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 )].

All identified pills

Side effects

6 ADVERSE REACTIONS 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 Cadila Pharmaceuticals Limited at 1-202-355-9785 or www.cadilapharma.com 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- Adverse Reactions Reported in >2% of Patients Treated with Tizanidine Tablets and Incidence Greater than Placebo Adverse Reaction P lacebo 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 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 P lacebo 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. 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

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