Dangerous Drug Interaction with Zanaflex (Aug. 2007)

Acorda Therapeutics recently alerted healthcare professionals about new contraindications for Zanaflex. Zanaflex (tizanidine) is used to treat spasticity. New labeling says that this drug should not be used concomitantly with either of two CYP1A2 inhibitors: fluvoxamine, which is used to treat depression and anxiety disorders, or the antibiotic ciprofloxacin. Taking either of these drugs together with tizanidine can cause dangerously elevated serum levels of tizanidine, which can lead to side effects such as severe hypotension and sedation. The company says that other CYP1A2 inhibitors may also lead to substantial increases in tizanidine blood concentrations, although there have been no clinical studies to substantiate this. Therefore, using tizanidine with other CYP1A2 inhibitors should ordinarily be avoided. These drugs include zileuton, other fluoroquinolones, antiarrythmics, H-2 blockers, oral contraceptives, acyclovir and ticlopidine. Additional Information: FDA MedWatch Safety Alert. Zanaflex (tizanidine hydrochloride) Tablets and Capsules. April 11, 2007. http://www.fda.gov/medwatch/safety/2007/safety07.htm#Zanaflex