Mircette

[desogestrel/ ethinyl estradiol and ethinyl estradiol]

TABLE I: MEAN (SD) PHARMACOKINETIC PARAMETERS OF Mircette ® OVER A 28-DAY DOSING PERIOD IN THE THIRD CYCLE (n= 17).
Etonogestrel
Day Dose * Cmax Tmax t1/ 2 AUC0Ð 24 CL/ F mg pg/ mL h h pg/ mL° hr L/ h
1 0.15 2503.6 (987.6) 2.4 (1.0) 29.8 (16.3) 17,832 (5674) 5.4 (2.5) 21 0.15 4091.2 (1186.2) 1.6 (0.7) 27.8 (7.2) 39,391 (12,134) 4.4 (1.4)
* Desogestrel
Ethinyl Estradiol
Day Dose Cmax Tmax t1/ 2 AUC0Ð 24 CL/ F mg pg/ mL h h pg/ mL° hr L/ h
1 0.02 51.9 (15.4) 2.9 (1.2) 16.5 (4.8) 566 (173) a 25.7 (9.1) 21 0.02 62.2 (25.9) 2.0 (0.8) 23.9 (25.5) 597 (127) a 35.1 (8.2)
24 0.01 24.6 (10.8) 2.4 (1.0) 18. 8 (10.3) 246 (65) 43.6 (12.2) 28 0.01 35.3 (27.5) 2.1 (1.3) 18. 9 (8.3) 312 (62) 33.2 (6.6)
a n= 16 Cmax Ð measured peak concentration Tmax Ð observed time of peak concentration t1/ 2 Ð elimination half-life, calculated by 0.693/ Kelim AUC0Ð 24 Ð area under the concentration-time curve calculated by the linear trapezoidal rule (Time 0 to 24 hours) CL/ F Ð apparent clearance

Distribution

Etonogestrel, the active metabolite of desogestrel, was found to be 99% protein bound, pri-marily to sex hormone-binding globulin (SHBG). Ethinyl estradiol is approximately 98.3% bound, mainly to plasma albumin. Ethinyl estradiol does not bind to SHBG, but induces SHBG synthesis. Desogestrel, in combination with ethinyl estradiol, does not counteract the estrogen-induced increase in SHBG, resulting in lower serum levels of free testosterone (96Ð 99).

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Metabolism

Desogestrel:

Desogestrel is rapidly and completely metabolized by hydroxylation in the intestinal mucosa and on first pass through the liver to etonogestrel. Other metabolites (i. e., 3 -OH-desogestrel, 3 -OH-desogestrel, and 3 -OH-5 -H-desogestrel) with no pharma-cologic actions also have been identified and these metabolites may undergo glucuronide and sulfate conjugation.

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