Pharmacokinetics, pharmacodynamics, and tolerability of cabergoline, a prolactin-lowering drug, after administration of increasing oral doses (0.5, 1.0, and 1.5 milligrams) in healthy male volunteers.

ABSTRACT

Cabergoline (CAB) a long-acting dopaminergic ergoline derivative, was given orally, in single doses of 0.5, 1.0, and 1.5 mg, to 12 healthy men in order to evaluate its PRL-lowering effect as well as its plasma pharmacokinetics and urinary excretion. Drug administrations were separated by 5-week washout periods. Blood samples for PRL and CAB determination were taken at baseline and for 840 h thereafter (every 1 h up to 4 h, every 4 h up to 12 h, every 24 h up to 168 h, and weekly up to 5 weeks). Fractional urine collections for CAB excretion were taken immediately before drug administration, every 4 h up to 12 h, and every 12 h up to 168 h. During the study period, blood pressure and heart rate were monitored at the same time periods of plasma sampling for CAB, and electrocardiographic tracings and hematological evaluations were performed before and after each treatment period. All CAB doses (0.5, 1.0, and 1.5 mg) produced in all subjects a complete PRL suppression (PRL < 1.0 micrograms/L), that occurred earlier and persisted longer with the two higher doses. PRL secretion areas [area under the curve (AUC) 0-48 h and 48-840 h] were higher after 0.5-mg than after 1.0- and 1.5-mg doses. In particular, in the first portion of the area, the difference between 0.5 mg and both 1.0 and 1.5 mg was highly statistically significant (P < 0.01) without significant differences between the two highest doses. Mean CAB maximal plasma concentrations (Cmax) were 33.3 +/- 3.69, 40.3 +/- 2.49, and 67.0 +/- 9.79 ng/L after 0.5, 1.0, and 1.5 mg CAB, respectively; time to Cmax was 2 h (median) for all doses; CAB AUC(0-168 h) after 0.5 mg CAB was significantly lower (P < 0.01) than after 1.5 mg CAB. The percentages of the administered doses of CAB excreted in urine were 1.1 +/- 0.1%, 1.1 +/- 0.1%, and 1.2 +/- 0.1% for the 0.5-, 1.0-, and 1.5 mg doses, respectively (P = NS). CAB AUCs(0-168 h) and Cmax normalized to the 1.0-mg dose were compared by two-way analysis of variance; no significant differences were found for CAB AUCs(0-168h); Cmax after 0.5 mg was significantly higher (P < 0.01) than after 1.0 and 1.5 mg CAB. A progressive decrease of systolic and diastolic blood pressure was observed, and symptomatic hypotension after the 1.0-mg dose did not allow one subject to receive the 1.5-mg dose. Other mild to moderate adverse events occurred only after 1.0 and 1.5 mg CAB. These results indicate that, in the dose range of 0.5-1.5 mg, the pharmacokinetics of CAB are dose independent, and that the pharmacodynamic data and the frequencies of adverse events of CAB are dose related, with no significant differences in the PRL-lowering effect of the 1.0- and 1.5-mg doses.