Pharmacokinetics of etonogestrel and ethinylestradiol released from a combined contraceptive vaginal ring.

Author(s): Timmer CJ, Mulders TM

Affiliation(s): Department of Drug Metabolism and Kinetics, NV Organon, Oss, The Netherlands. c.timmer@organon.oss.akzonobel.nl

Publication date & source: 2000-09, Clin Pharmacokinet., 39(3):233-42.

Publication type: Clinical Trial; Randomized Controlled Trial

OBJECTIVE: To assess the pharmacokinetics of etonogestrel and ethinylestradiol released from a novel combined contraceptive vaginal ring (NuvaRing) releasing etonogestrel 120microg and ethinylestradiol 15 microg per day and compare them with those of a combined oral contraceptive containing desogestrel 150 microg/ethinylestradiol 30 microg (DSG/EE COC). DESIGN AND SETTING: This was a nonblind, randomised, crossover study in 16 healthy women. METHODS: All volunteers received one cycle of DSG/EE COC before being randomised to 1 of 2 treatment groups. The participants in group 1 received 1 cycle of DSG/EE COC, a treatment period with NuvaRing and an intravenous bolus injection of etonogestrel/ethinylestradiol (150 microg/30 microg). Those in group 2 received a NuvaRing treatment period, 1 cycle of DSG/EE COC and the same intravenous bolus injection. RESULTS AND CONCLUSIONS: After the insertion of NuvaRing, maximum serum concentrations of etonogestrel and ethinylestradiol were achieved in approximately 1 week. The concentrations subsequently showed a gradual linear decrease in time. The maximum serum concentrations of etonogestrel and ethinylestradiol were approximately 40 and 30%, respectively, of those for the DSG/EE COC. In comparison with the DSG/EE COC, the absolute bioavailability for NuvaRing was higher for etonogestrel (102.9 vs 79.2%) and similar for ethinylestradiol (55.6 vs 53.8%). Taking the difference in daily doses into account, systemic exposure to etonogestrel was similar for NuvaRing and the DSG/EE COC, whereas systemic exposure to ethinylestradiol with NuvaRing was only approximately 50% of that for the DSG/EE COC.