guanabenz and Zanaflex Interactions

Interactions between guanabenz and Zanaflex (tizanidine)

guanabenz and tizanidine (Major Drug-Drug)

GENERALLY AVOID: Tizanidine has alpha-2 adrenergic activity and may potentiate the hypotensive effects of other alpha-2 adrenergic agonists. Pharmacologic studies have found tizanidine to possess between 1/10 to 1/50 of the potency of clonidine, a structurally similar agent, in lowering blood pressure. In a single-dose study where blood pressure was monitored closely after dosing, two-thirds of patients treated with an 8 mg dose had a 20% reduction in either the diastolic or systolic blood pressure. The reduction was seen within 1 hour after dosing, peaked 2 to 3 hours after dosing, and was associated at times with bradycardia, orthostatic hypotension, lightheadedness, dizziness, and rarely, syncope. The hypotensive effect of tizanidine is dose-related and has been measured following single doses of 2 mg or more.

MANAGEMENT: Concomitant use of tizanidine with other alpha-2 adrenergic agonists should be avoided.