ORAL-ADMINISTRATION OF METHYLERGOMETRINE SHOWS A LATE AND UNPREDICTABLE EFFECT ON THE NONPREGNANT HUMAN MENSTRUATING UTERUS

Objective: To study the pharmacodynamic and pharmacokinetic properties of oral and intravenous methylergometrine upon uterine motility durin g menstruation. Study-design: Intra-uterine pressure was measured in s ix volunteers with a fluid-filled sponge-tipped catheter during menstr uation. Methylergometrine was given orally (0.5 mg) or intravenously ( 0.2 mg) in a cross-over design. Results: After intravenous administrat ion, a fast increase of the frequency of uterine contractions and basa l tone occurred with a decrease of amplitude, lasting at least 30 min. Oral administration had a late and less marked effect on uterine moti lity. An intravenous dose administered 24 h after an oral dose had no effect on uterine motility. Pharmacokinetic data, such as the maximum plasma concentration (C-max), the time at which C-max is reached (t(ma x)) and the half-life of absorption (t(1/2abs)) also demonstrated larg e individual variations after oral administration. Conclusion: Oral ad ministration of methylergometrine had an unpredictable and late effect on uterine motility on the menstruating uterus, probably due to an un predictable bioavailability, in contrast with the fast and predictable effect after intravenous administration.