Possible Interaction: Cocaine and Phenoxybenzamine

“Before phenoxybenzamine infusion, cocaine 2.0 mg/kg produced a 53% increase in maternal mean arterial pressure (MAP), a 50% reduction in total uterine blood flow, and a 191% increase in uterine vascular resistance.”

“Norepinephrine (20 micronM) or cocaine (29 micronM) afforded no protection against DMI-induced 3H-norepinephrine uptake blockade, but both agents significantly protected against blockade of PBZ.”

“These authors, using rat vasa deferentia, showed that cocaine caused an increase in the maximum response of tissues which had been treated with an irreversible antagonist ( phenoxybenzamine ), at a dose sufficient to reduce the maximum response to noradrenaline.”

“2 Phenoxybenzamine (30 μm) or phentolamine (36 μm) plus cocaine (13 μm) caused a considerable increase in the noradrenaline output.”

“At least a 30-fold greater concentration of both phenoxybenzamine and cocaine is required to induce release of 3 H-NE than is required to inhibit uptake of the catecholamines.”

“ Cocaine and phenoxybenzamine are equipotent in inhibiting removal of 3 H-NE ; phentolamine is approximately 100 times less potent.”

“2 Without flow‐stop, NA output was 0·93±0·25 ng/stimulus, which was significantly increased after cocaine (123±6·6%), phentolamine (415±93%) and phenoxybenzamine (578±107%).”

“ Phenoxybenzamine blocked the response of the nictitating membrane to norepinephrine after cocaine or after chronic treatment of animals with reserpine.”

“These responses were incompletely and reversibly inhibited by cocaine , but completely and irreversibly blocked by phenoxybenzamine.”