Comparison of metabolic and clinical effects of four oral contraceptive formulations and a contraceptive vaginal ring.

A group of 100 women desiring OC received one of the following four formulations on a randomized basis: (1) mestranol 50 micrograms and norethindrone 1 mg, , (2) ethinyl estradiol 50 micrograms and norethindrone 1 mg, (3) ethinyl estradiol 35 micrograms and norethindrone 1 mg, and (4) ethinyl estradiol 30 micrograms and levonorgestrel 150 mg. An additional 10 women received a CVR containing levonorgestrel and estradiol. Measurement of a large number of serum chemistries, lipids, proteins, clotting factors, and liver enzymes was obtained before and 3 and 6 months after starting medication. Clinical factors such as weight, blood pressure, bleeding or spotting, or any adverse side effects were also recorded. There was no significant difference in the metabolic parameters measured among the four oral contraceptives except the increase in angiotensinogen was slightly less in the groups receiving the compounds with 30 or 35 micrograms estrogen and the groups receiving the norgestrel compound had no increase in triglycerides and a slight decrease in cholesterol levels. When the CVR was compared with all oral contraceptives it was found to produce no change in angiotensinogen levels and a decrease in triglycerides. Some of each group of OC users had a lowering of antithrombin III to abnormal levels but none of the CVR users had his amount of decrease. As oral steroids with 30 or 35 micrograms of estrogen do not produce significantly less metabolic alteration than do compounds with 50 micrograms of estrogen, it is unlikely that their use will reduce the incidence of the uncommon serious adverse effects associated with OC use. However, since the CVR's did not increase angiotensinogen, their use as contraceptives will most likely not produce hypertension and possibly the other serious circulatory problems which are increased in some OC users.