INFLUENCE OF THE DOSING INTERVAL ON PROLACTIN-RELEASE AFTER REMOXIPRIDE

1 The prolactin response following administration of the D-2-dopamine receptor antagonist remoxipride was studied in eight healthy male volu nteers. The purpose of the study was to investigate the duration of a refractory period of prolactin release following two doses of remoxipr ide. A further aim was to compare the prolactin response following rem oxipride and thyrotropin release hormone (TRH) during the refractory p eriod. The subjects received two 30 min intravenous (i.v.) infusions o f remoxipride 50 mg with different time intervals between the two dose s, in a randomized six period crossover design. The time intervals bet ween the two remoxipride doses were 2, 8, 12, 24 and 48 h. On one occa sion the remoxipride dose was followed by an i.v. injection of TRH aft er 2 h. 2 The plasma peak prolactin concentrations obtained after the first remoxipride dose correspond to a maximal release of prolactin ac cording to earlier studies. A small second peak of prolactin was obser ved after 2 h. The release was gradually increased with longer time in tervals between the consecutive doses. The refractory period for a sec ond prolactin release similar to the first one after remoxipride was f ound to be 24 h for most of the subjects. 3 TRH resulted in a faster a nd higher increase in prolactin response of a shorter duration than af ter remoxipride administered 2 h after the first dose.