Pharmacokinetics of different doses of norethisterone oenanthate.

Doses of norethisterone oenanthate of 300, 150, 100 and 50 mg were administered to four groups of subjects. Due to wide intersubject variations there were no statistically significant differences in the pharmacokinetic parameters for the different groups but there were significant correlations between the dose and the mean values for these parameters. There was little difference between the groups in the duration for which ovarian function was suppressed due to the inter-subject variation being greater than the inter-dose effect. The duration of the antifertility action of norethisterone oenanthate cannot be increased by increasing the dose above the standard 200 mg; however, with an injection interval of 60 to 70 days, it seems likely that the dose could be reduced to 150 mg.