A study of interaction of a low-dose combination oral contraceptive with anti-tubercular drugs.

Low-dose combination contraceptive (containing norethisterone acetate 1 mg and ethinyl estradiol 30 micrograms) was administered to women receiving concurrent therapy with either Rifampicin or "triple" antitubercular treatment consisting of paraaminosalicylic acid (PAS), isonicotinic acid hydrazide (INH) and streptomycin. Plasma levels of norethisterone (NET) and ethinyl estradiol (EE), PAS and INH were measured and the area under curve (AUC) was calculated for NET and EE. Rifampicin treatment (9 women) caused a statistically significant reduction of the plasma NET levels as well as the AUC of NET. In this group of women, though a trend for reduction in EE levels was observed in individual subjects, it was not statistically significant. Out of 7 regularly menstruating women on Rifampicin therapy, 2 showed a premenstrual rise of plasma progesterone (P) levels (> 4 ng/ml) suggesting an ovulatory cycle and 3 experienced menstrual irregularities. In contrast, plasma levels of NET and EE as well as their AUCs were not altered in 8 women receiving "triple" antitubercular therapy. Only one woman out of 8, had menstrual irregularity and all women had P levels in the anovulatory range. Furthermore, oral contraceptive treatment did not alter the plasma levels of PAS and INH.

Intravaginal contraception with the synthetic progestin, R2010.

Four women used polysiloxane vaginal rings of core design containing 50 mg of norgestrienone (17 alpha-ethynyl-17 beta-hydroxy-estra-4,9,11,trien-3-one). The treatment was given in three-week cycles, leaving one treatment-free week between the cycles. The patterns of bleeding were registered and plasma norgestrienone (R2010), estradiol, progesterone, and gonadotropins were determined. Altogether twelve cycles were studied. The patterns of bleeding were unsatisfactory; only one subject had regular bleedings, and two of these were preceded by a luteal phase. The mean plasma concentration of norgestrienone (R2010) produced by the rings was 0.9 ng/ml. Ovulation was observed in 25% of cycles studied. Some follicular activity was present in every subject as judged by estradiol peaks. Excluding LH peaks in subjects who ovulated, mild pituitary suppression was achieved by this treatment. The only side-effect complained of was acne in one subject. The ring was regarded as easy to use.

PIP: The clinical performance as well as effects on gonadal and pituitary functions were analyzed during use of a contraceptive vaginal ring (CVR) impregnated with R2010, a synthetic progestin. 4 regularly menstruating women aged 25-29 years, who were parous and married, volunteered, and treatment was given in 3-week periods, leaving 1 treatment-free week. The CVR was a polysiloxane ring of core design and contain 50 mg of norgestrienone. Bleeding patterns were registered along with plasma R2010, progesterone, estradiol, and gonadotropins (luteinizing and follicle stimulating hormones). A total of 12 cycles were studied for this investigation. Bleeding patterns were unsatisfactory. Only 1 of 4 subjects had regular, simulated menstrual bleedings; 2 of these bleedings were preceded by a luteal phase (according to hormone assays). Mean plasma concentration of the progestin produced by the rings was .9 ng/ml. In 25% of the cycles ovulation was observed; in addition, some follicular activity was present in all 4 subjects, based on measurement of estradiol peaks. Mild pituitary suppression was achieved in the 3 subjects who did not ovulate. An acne flare-up constituted the only reported side effect.

Release of contraceptive steroids from sustained release dosage forms and resulting plasma levels.

The correlations of plasma levels of levonorgestrel, megestrol acetate and norgestrienone with the doses delivered from subdermal implants and contraceptive rings have been examined. Differences in plasma levels as large as three-fold between different subjects receiving nearly identical doses were observed with all three steroids. The relative plasma levels seen from one subject to another showed high consistency over time. Part of the explanation may lie in differing levels of sex hormone binding globulin, but additional factors must be operative since megestrol acetate binds only weakly with this carrier.