Prescribers Warned of Tizanidine Drug Interactions

Concomitant use of fluvoxamine or ciprofloxacin with tizanidine HCl (Zanaflex capsules and tablets, Accorda Therapeutics) is contraindicated, the FDA warned healthcare professionals yesterday. Tizanidine is a short-acting drug for the management of spasticity.Data from pharmacokinetic studies shows that coadministration of these potent cytochrome P-450 isoenzyme 1A2 (CYP 1A2) inhibitors resulted in significantly increased serum levels of tizanidine and potentiated its hypotensive and sedative effects, according to an alert from MedWatch, the FDA's safety information and adverse event reporting program. Because of the potential drug interaction, concomitant use of other CYP 1A2 inhibitors should generally be avoided and approached with caution if clinically necessary. Safety labeling revisions to incorporate this information in the tizanidine prescribing monograph were originally approved by the FDA on July 28, 2006, and conveyed to prescribers via letter from the company on March 5, 2007.