Variation in Bioavailability of Oral Methylergometrine in Healthy Male Volunteers

The aim of this investigation was to assess the pharmacokinetics and bioavail-ability of methylergometrine in 6 healthy male volunteers after an oral dose of 0.125mg and after an intravenous dose of 0.200mg. A large variation in bio-availability of between 22 and 136% (mean value 84.9 ± 37.2%) was observed in the 6 volunteers. The lag time was also subject-dependent and ranged between 0.24 and 0.50 hours. After intravenous administration, the pharmacokinetic profile could be described with a 2-compartment model. The distribution half-life (t½α) was 0.19 ± 0.27 hours, the elimination half-life (β) was 1.85 ± 0.28 hours, total body clearance (CL) amounted to 34.1 ± 9.7 L/ h, and the steady-state volume of distribution (Vss) was 71.5 ± 25.9L. After oral administration, the pharmacokinetic profile could be described with a 1 -compartment model. The absorption half-life (t½abs) was 0.08 ± 0.08 hours, and the elimination half-life (t½β) was 2.08 ± 0.43 hours. This study with oral methylergometrine demonstrated such large interindividual variability in bioavailability that from a pharmacokinetic point of view the oral route of administration does not appear to be the most reliable way for accurate dosing in the prevention of postpartum haemorrhage.