Possible Interaction: Epinephrine and Phenoxybenzamine

“ Phenoxybenzamine (0.1 mM), an alpha-receptor blocking drug, and 0.5 … aspirin, an inhibitor of prostaglandin (PG) synthesis, inhibited the action of adrenaline , whereas 0.1 mM propranolol, a beta-receptor blocker, and 0.5 mM indomethacin, another inhibitor of the formation of PG, failed to do so.”

“After propranolol, noradrenaline and adrenaline consistently produced contraction which was blocked by phenoxybenzamine 0.1 μg/ml.”

“2 Since phentolamine or phenoxybenzamine inhibited the contractions induced by adrenaline or noradrenaline in the presence of oxprenolol, it is assumed that the contractions are caused by stimulation of excitatory α‐adrenoceptors.”

“The bronchoconstrictor effect of adrenaline and noradrenaline was not affected by atropine but was inhibited by phenoxybenzamine or dibenamine (1–2 mg/kg).”

“The constrictor effect of adrenaline and noradrenaline was antagonized or completely inhibited by the α-receptor blocking agents phenoxy-benzamine and dibenamine in a concentration of 1–5 μg/ml.”

“In rabbit isolated atria, cocaine, guanethidine and phenoxybenzamine increased the changes in rate and force of contractions caused by noradrenaline and adrenaline , but did not potentiate isoprenaline.”

“The vasodilatation and hypotension induced by POB in the postoperative period is often refractory to high doses of conventional -adrenergic drugs such as epinephrine and norepinephrine, and an infusion of arginine vasopressin is often necessary (7,8).”

“ Phenoxybenzamine prevented vasoconstriction in response to epinephrine , dopamine, and phenylephrine, with its effect lasting at least 5 hours.”

“ Phenoxybenzamine , an alpha-adrenoceptor antagonist, canceled this potentiation by epinephrine.”

“Alpha-receptor blocking agents, phenoxybenzamine and indoramine, showed an inhibition of the contraction induced with both epinephrine and norepinephrine.”

“1 The distribution of alpha- and beta-adrenoceptors in isolated preparations … human bladder neck and detrusor muscle has been studied.2 Adrenaline caused contraction of the bladder … which was blocked by phenoxybenzamine but unaltered by propranolol.3 Isoprenaline caused relaxation of the bladder neck which was blocked by propranolol.”