Zanaflex Contraindications/Precautions
- abrupt discontinuation
- breast-feeding
- children
- driving or operating machinery
- elderly
- hepatic disease
- hepatic encephalopathy
- hepatitis
- hypotension
- pregnancy
- psychosis
- renal failure
- renal impairment
Zanaflex (Tizanidine) Contraindications/Precautions
Tizanidine is contraindicated in patients with known hypersensitivity to tizanidine or its ingredients.
Tizanidine is a central-acting alpha2-adrenergic agonist which is structurally and pharmacologically related to clonidine. Although tizanidine has a lower propensity to lower blood pressure than clonidine (2-10% of the antihypertensive potency in animal models), it can result in significant hypotension in some patients, especially with higher doses. Caution is advised when tizanidine is to be used in patients at risk for developing hypotension including patients who are receiving concurrent antihypertensive therapy.
Tizanidine should be used with caution in elderly patients because drug clearance may be decreased four-fold. Tizanidine should also be used with caution in patients with renal impairment (CrCl < 25 ml/min) or renal failure, as clearance is reduced by more than 50%. In these patients, during titration, the individual doses should be reduced. These patients should be monitored closely for the onset or increase in severity of the common adverse events (dry mouth, somnolence, asthenia and dizziness) as potential indicators of excessive overdose.
Due to the potential for hepatotoxicity, monitoring of aminotransferase levels is recommended during the first 6 months of tizanidine therapy (e.g., baseline, 1, 3 and 6 months) and periodically thereafter, based on clinical status. Tizanidine should be avoided or used with extreme caution in patients with hepatic impairment or hepatic disease (e.g., cirrhosis, hepatic encephalopathy, hepatitis). Tizanidine has not been studied in patients with hepatic disease.
Tizanidine can cause drowsiness and sedation. Patients receiving tizanidine should be advised to avoid driving or operating machinery until the effects of the drug are known.
Tizanidine use has been associated with hallucinations; tizanidine should be used with caution in patients with psychosis.
There is limited experience reported with abrupt discontinuation of tizanidine. Abrupt withdrawal of tizanidine after 6 weeks of therapy in multiple sclerosis patients was not associated with adverse effects related to drug dependence. However, increased spasticity was reported which was treated by reinstitution of therapy and gradual dose reduction. Abrupt cessation of tizanidine in monkeys produced transient signs of withdrawal at doses > 35 times the maximum recommended human dose on a mg/m2 basis; these transient withdrawal signs (increased locomotion, body twitching, and aversive behavior) were not reversed by naloxone administration. Until more data are available, use caution when abruptly stopping therapy with tizanidine. If tizanidine therapy needs to be discontinued, especially in patients receiving high doses for long periods, the manufacturer recommends gradually reducing the dose to minimize the risk of withdrawal and rebound hypertension, tachycardia, and hypertonia.
Tizanidine should be used with caution where spasticity is utilized to obtain increased function or to sustain posture and balance during movement.
Tizanidine is classified as an FDA pregnancy category C drug. Tizanidine has not been studied in pregnant women. Tizanidine should be given to pregnant women only if clearly needed. The effect of tizanidine on labor and delivery in humans is unknown.
It is not known whether tizanidine is excreted into human breast milk, although as a lipid soluble drug, it might be expected to pass into breast milk. Tizanidine should be used with caution in breast-feeding women. A decision should be made to discontinue nursing or to discontinue the drug, considering the therapeutic benefits for the mother.
The safety and efficacy of tizanidine are not established in children.
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