AIMTo quantify progesterone (P) and one of its metabolites 20alpha-hydroxy-4-pregnen-3-one (20alpha-OHP) in rat plasma and uterus after im administration of progesterone.

METHODSPlasma and uterus samples were prepared by liquid-liquid extraction and separated through Shimadzu VP-ODS column (150 mm x 4.6 mm ID, 5 microm). The mobile phase consisted of acetonitrile and water (60: 40, adjusted to pH 4.0 with phosphoric acid). The detector was set at 240 nm. Norgestrel was used as the internal standard.

RESULTSCmax of P in plasma was (508 +/- 62) microg x L(-1), Tmax was (3.2 +/- 0.4) h, T1/2 (ke) was (10 +/- 4) h and mean AUC0-48h was (5886 +/- 1573) microg x L(-1) x h. The maximum concentration of P in uterus was (1.7 +/- 1.1) microg x g(-1) and the peak time was (5.2 +/- 1.11) h. 20alpha-OHP showed a similar Tmax with P.

CONCLUSIONThe method is accurate and convenient. It can be used to determine P and its main metabolite 20alpha-OHP simultaneously for studying their preclinical pharmacokinetics.

20-alpha-Dihydroprogesterone ; blood ; pharmacokinetics ; Animals ; Area Under Curve ; Chromatography, High Pressure Liquid ; methods ; Female ; Injections, Intramuscular ; Progesterone ; blood ; metabolism ; pharmacokinetics ; Rats ; Rats, Wistar ; Uterus ; metabolism