Original Article

Pharmacokinetics of norethindrone oenanthate in 5 women after a single dose of norethindrone oenanthate and estradiol valerate

Guo-wei SANG, Xin-hua LIU


The pharmacokinetics of norethindrone oenanthate (NET-OEN) and norethindrone (NET) were studied in 5 healthy Chinese women after a single im injection of NET-OEN 50 mg+estradiol valerate (EV) 5 mg in 1 ml peanut oil: benzyl benzoate 6:4 v/v. Peak levels of NET and NET-OEN in all women reached within 5 d, the mean peak values for NET and NET-OEN were 4.6 and 1.2 ng/ml; respectively. The apparent elimination rate constants (K) were calculated as 0.15 d-1 and 0.25 d-1 for NET and NET-OEN. The apparent elimination half-lives were 4.6 and 3.1 d for NET and NET-OEN, respectively. There was a significant correlation between the elimination half-life and peak values for NET. The time required for the serum steroid concentration to decrease below 100 pg/ml were 32+/-4 d for NET, and 14+/-6 d for NET-OEN. There was a 1.5 fold variation among the women in the bioavailability of NET. After im injection, 96.5% of bioavailable NET was released within 30 d.

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