Inhibition of basal and metoclopramide-induced prolactin release by cabergoline, an extremely long-acting dopaminergic drug.

The aim of this study was to evaluate the effectiveness of the ergoline derivative cabergoline in inhibiting the serum PRL response to metoclopramide (MCP; 5 mg, iv) and the duration of this effect. Seven normal men received cabergoline (600 micrograms, orally) on day 0 and underwent a MCP test on days -1, 1, 4, 8, 15, and 28. Fasting serum PRL levels were significantly depressed from days 1-14; the nadir value occurred on day 4. MCP-induced PRL release was significantly inhibited up to day 28, with a nadir on day 4. Two months later, four of the men received placebo on day 0, and tests with MCP were performed on days -1, 8, and 28; basal serum PRL levels and PRL responses to MCP were superimposable on days -1, 8, and 28. These data indicate that cabergoline is an effective long-acting inhibitor of PRL release in normal men, suitable for use in the management of hyperprolactinemic patients.