Prolactin lowering effect of dihydroergokryptine in rat and in man

The prolactin lowering activity of dihydroergokryptine was investigated both in rats and in humans. The drug was administered orally at the doses of 0.2, 1 and 5 mg/Kg to intact or reserpinized male rats. Nine male adult volunteers were given 300 mg cimetidine iv 90 min after receiving 2, 3 or 4.5 mg of dihydroergokryptine and 3, 4.5 and 6.75 mg of dihydroergocristine or placebo per os in a randomized, cross-over design. Eight young adult males were injected im with 10 mg sulpiride 120 min after randomly receiving dihydroergokryptine 2.5 and 5 mg or placebo in a cross-over manner. Finally, five healthy young women were given dihydroergokryptine 2.5 and 5 mg, bromocriptine 2.5 mg and placebo in a cross-over design. Dihydroergokryptine caused a strong, long-lasting, dose-dependent fall of plasma prolactin concentrations in both rats and humans. Moreover, it inhibited the reserpine-induced rise of plasma prolactin in rats, as well as the cimetidine-or sulpiride-induced hyperprolactinemia in humans. Dihydroergokryptine proved twice as potent as dihydroergocristine and about half as potent as bromocriptine. Effective doses of both dihydrogenated ergot alkaloids were much better tolerated than bromocriptine.