Prolactin response following intravenous and oral sulpiride in healthy human subjects in relation to sulpiride concentrations.

Sulpiride (100 mg) was administered intravenously and orally to healthy human subjects. Serum concentrations of sulpiride and prolactin were followed for 36 h. Both routes of drug administration resulted in a pronounced and sustained increase in serum prolactin concentration. The prolactin response was positively correlated to the prolactin baseline value. The concentrations of prolactin remained at an elevated plateau for 9--36 h after drug treatment despite low drug concentrations. The level of this plateau was directly related to the normal circadian secretion of prolactin. The sustained prolactin elevation may be due to high affinity and strong binding of the compound to the regulating receptors or the formation of an active sulpiride metabolite. Prolactin and sulpiride concentrations were significantly correlated during the initial phase after intravenous sulpiride. Following intravenous and oral sulpiride the area under the concentration-time curve (AUC) for prolactin was similar despite a considerable difference in the sulpiride concentration.