Possible Interaction: Phenoxybenzamine and Yohimbine

“The IC50 (100 nM) derived from the blockade of [3H]yohimbine binding by phenoxybenzamine was significantly less than the IC50 (550 nM) for the corresponding reversal by phenoxybenzamine of the effects of norepinephrine on cyclic AMP accumulation.”

“We found that [3H]prazosin did not identify alpha 1-adrenergic receptors on platelets, and that phenoxybenzamine only inhibited [3H]yohimbine and [3H]DHE binding at higher concentrations than usually observed for alpha 1-adrenergic receptors.”

“pretreatment of rats with yohimbine , an α2-adrenergic antagonist, and was antagonized by pretreatment with phenoxybenzamine , an α1-adrenergic antagonist.”

“In contrast to phenoxybenzamine alone, exposure to phenoxybenzamine 10 μmol/1 in the presence of either clonidine 100 pmol/1 or yohimbine 10 μmol/1 failed to abolish the effects of the test compounds noradrenaline 0.1 μmol/1 and yohimbine 1 μmol/1, although the effects were reduced.”

“In the pithed rat, after 0.05 mg/kg phenoxybenzamine, prazosin caused a displacement of the dose-response curve of cirazoline to … than that caused by yohimbine; after 0.3 mg/kg phenoxybenzamine, prazosin and yohimbine caused about equal displacements; after 1 mg/kg phenoxybenzamine, yohimbine caused a … effect.”

“ Phenoxybenzamine can selectively eliminate the s-IPSP, in the presence of anti-cholinesterases that enhance s-IPSP and s-EPSP; and the alpha 2-antagonist, yohimbine , can partially but consistently depress s-IPSP selectively.”

“3 Yohimbine , prazosin and phentolamine partially protected against irreversible blockade by phenoxybenzamine.”

“When animals were simultaneously exposed to light and administered clonidine, the rapid reduction in NAT activity was affected only when animals were pretreated with both yohimbine and phenoxybenzamine.”

“Clonidine plus phenoxybenzamine inhibited the synthesis and utilization of dopamine and the combination also partly antagonized the effects of yohimbine on the trunover of dopamine.”

“The potentiating effect of NE on both responses was depressed with the pre-treatment of adrenergic α-blocking agents such as tolazoline, phenoxybenzamine, yohimbine and hydergine.”