This has been one of the most helpful medications for my spasms. If you are taking it you may want to be aware of this.
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MedWatch - The FDA Safety Information and Adverse Event Reporting Program

Acorda Therapeutics and FDA informed healthcare professionals of changes
to the CONTRAINDICATIONS and WARNINGS Sections of the product labeling
for Zanaflex, a drug used to treat spasticity, In pharmacokinetic
studies where tizanidine was coadministered with either fluvoxamine or
ciprofloxacin (CYP1A2 inhibitors), the serum concentration of tizanidine
was significantly increased and potentiated its hypotensive and sedative
effects. Although there are no clinical studies evaluating the effects
of other CYP1A2 inhibitors on tizanidine, coadministration of tizanidine
with other CYP1A2 inhibitors (zileuton, other fluroquinolones,
antiarrythmics, cimetidine, famotidine, oral contraceptives, acyclovir
and ticlopidine) should be avoided.

Read the complete MedWatch 2007 Safety summary, including a link to the
manufacturer's Dear Healthcare Provider Letter regarding this issue at:
http://www.fda.gov/medwatch/safety/2...7.htm#Zanaflex