The pharmacokinetics of steroïds used in estroprogestative contraception.

Christian Jamin

Service Gynécologie Obstétrique, CHU Bichat, Paris, France

Since the day contraceptives were marketed, the tendency has been to lower steroids doses which, one hoped, would lower secondary effects and improve tolerance.

At first improvements were spectacular but then, due to the rarity of secondary effects, results became difficult to measure. The contraceptive effect of low dose products depends mainly on progestins, which dose reaches a bottom level due to its blocking power. The progestin dose determines the oestrogen dose and the adequacy of their proportions as well as the quality of cycle control. With the progestins available today, the minimum estrogen dose is 20 micrograms per day for a 21 days cycle.

It has been possible to further diminish the dose of progestins, and consequently of estrogens, by increasing the duration of treatment to 24 days per cycle, with a slight deterioration of cycle control. The cutaneous way of administration by patch did not change this last point. However the vaginal way with a ring has given circulating levels and areas under the steroids curve equivalent to those of a 15 micrograms pill, but this time with an improvement of cycle control. Besides, circulating levels are remarkably stable with this ring.

Although studies are rarely comparative, general tolerance also seems to have been improved.