Complete adverse effect profile including incidence rates and management
Important Safety Information
This is not a complete list of all possible side effects. Contact your healthcare provider if you experience any unexpected symptoms. For serious or life-threatening side effects, seek emergency medical attention immediately.
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 )] 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 Covis Pharma at 1-866-488-4423 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.
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.
5 WARNINGS AND PRECAUTIONS Hypotension: monitor for signs and symptoms of hypotension, in particular in patients receiving concurrent antihypertensives;
Zanaflex should not be used with other α 2 -adrenergic agonists ( 5.1 , 7.7 ) Risk of liver injury: monitor ALTs;
discontinue Zanaflex if liver injury occurs ( 5.2 ) Sedation: Zanaflex may interfere with everyday activities;
sedative effects of Zanaflex, alcohol, and other CNS depressants are additive ( 5.3 , 7.5 , 7.6 ) Hallucinations: consider discontinuation of Zanaflex ( 5.4 ) Less potent inhibitors of CYP1A2: may cause hypotension, bradycardia, or excessive drowsiness, use caution if Zanaflex is used with less potent inhibitors of CYP1A2, e.g., zileuton, other fluoroquinolones, antiarrhythmics, cimetidine, famotidine, oral contraceptives, acyclovir, and ticlopidine ( 5.5 , 7.3 , 12.3 ) Renal impairment (creatinine clearance < 25 mL/min): use Zanaflex with caution, and monitor closely for dry mouth, somnolence, asthenia and dizziness as indicators of potential overdose ( 5.7 ) 5.1 Hypotension Tizanidine is an α 2 -adrenergic agonist that can produce hypotension.
Syncope has been reported in the post marketing setting.
Like all medications, Zanaflex can cause side effects. However, not everyone who takes this medication will experience them. Many side effects are dose-dependent and may improve as your body adjusts to the medication. Others may require dose adjustment or medical attention.
Contact your healthcare provider promptly if you experience:
Seek immediate emergency medical care if you experience signs of: