Possible Interaction: Tizanidine and Yohimbine

“Idazoxan (I1, I2, I3, and alpha2), efaroxan (I1, I3, and alpha2), and RX821002 (I3 and alpha2), but not yohimbine , an alpha2-adrenergic receptor antagonist with no affinity for I receptors, antagonized the inhibitory effects of tizanidine.”

“In the second part of the study, after pretreatment with yohimbine , an alpha-2 adrenergic receptor blocker, at the dose of 2 mg/kg, anticonvulsant effect of tizanidine is diminished.”

“The blockade of alpha 2-adrenoceptors with yohimbine or phentolamine counteracted the protection induced by tizanidine.”

“These effects of TIZ on M-dependent ileum were antagonized by the alpha 2-adrenoceptor antagonist yohimbine.”

“Exposure of the cord … microM clonidine and tizanidine significantly reduced the release of substance P. The inhibitory effects of clonidine and tizanidine were attenuated by pre-exposure of … 10 microM piperoxane, which has alpha 2-antagonistic activity and the inhibitory effect of clonidine was attenuated by 10 microM yohimbine.”

“The action of tizanidine was antagonized by the alpha 2-adrenoreceptor antagonist, yohimbine , but not by the alpha 1 antagonist prazosin, nor by dopamine, serotonin and GABA receptor antagonists.”

“The action of tizanidine and clonidine was completely antagonized by pretreatment with yohimbine , an alpha 2-adrenoceptor blocker, but not by prazosin, an alpha 1-adrenoceptor blocker.”

“ Yohimbine and phentolamine reduced the inhibition of TRH-stimulated acid secretion by tizanidine.”

“The preferential depressant actions of tizanidine , noradrenaline and clonidine were antagonized by the selective alpha 2-antagonist RX781094 administered iontophoretically at the same site as the agonists, and by intravenously administered yohimbine.”

“Pretreatment with the alpha 2-blocker yohimbine antagonized the depressant action of tizanidine in intact rats whereas the alpha 1-blocker prazosin antagonized the facilitatory action of tizanidine in the spinalized rats.”