Tizanidine Side Effects
Some side effects of tizanidine may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA.
For the Consumer
Applies to tizanidine: oral capsule, oral tablet
Get emergency medical help if you have any of these signs of an allergic reaction while taking tizanidine: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.
Call your doctor at once if you have any of these serious side effects:
feeling light-headed, fainting, slow heart rate;
hallucinations, confusion, unusual thoughts or behavior;
nausea, stomach pain, low fever, loss of appetite, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes); or
burning or pain when you urinate.
Less serious side effects may be more likely to occur, such as:
drowsiness or dizziness;
feeling anxious or nervous;
numbness or tingling;
stomach pain, diarrhea, constipation, vomiting;
muscle weakness, back pain;
increased muscle tone or spasms; or
sweating or skin rash.
This is not a complete list of side effects and others may occur. Tell your doctor about any unusual or bothersome side effect.
For Healthcare Professionals
Applies to tizanidine: oral capsule, oral tablet
Visual hallucinations were observed in 3% (n=5) of patients in 2 clinical trials. Patients were aware the events were not real in most cases, and in only one case did problems persist following discontinuation. Sedation appears to be dose related in single dose studies and may in approximately 10% of cases be severe enough to interfere with daily activities. In multiple dose studies, however, the incidence of sedation peaked following one week of treatment, and remained stable thereafter.
Nervous system side effects have frequently been associated with the use of this tizanidine. Sedation, somnolence, and asthenia have been reported in up to 48% of patients. Dizziness has been reported in 16% of patients. Duskiness, hallucinations, nervousness, insomnia, and speech disorder have been reported rarely.
Gastrointestinal side effects have included dry mouth in approximately 50% and constipation or vomiting in less than 4% of patients.
Most cases of elevated liver function tests in patients receiving tizanidine rapidly resolved upon removal of the medication. Of the three deaths reported, two patients had symptoms of liver disease following 2 months of treatment while one occurred following 11 days. Two of the patients were receiving other medications that have been associated with hepatic toxicity.
Hepatic side effects associated with the use of tizanidine have included elevations of liver function tests to greater than 3 times the upper normal limit in 5% of patients. Three deaths associated with liver failure have been reported during postmarketing surveillance in patients receiving tizanidine.
Cardiovascular side effects have included hypotension and bradycardia. Rarely, severe hypotension associated with use of this drug has required IV fluids, epinephrine, and dopamine.
The manufacturer reports a single dose study that found hypotension in 16% and 30% of patients following an 8 and 16 mg dose, respectively. The occurrence of bradycardia under the same circumstances was 2% and 10%.
Ocular side effects including blurred vision have been reported rarely.
Dermatologic side effects have been isolated to rashes.
Other side effects have included three cases of rebound symptoms on sudden withdrawal of tizanidine. Withdrawal symptoms included hypertension, tachycardia, hypertonia, tremor, and anxiety.
The withdrawal case reports suggested that these patients were also misusing narcotics.
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