C. Brandon Chenault

Comparative studies of the ethynyl estrogens used in oral contraceptives

Ethynyestradiol and mestranol, in doses ranging from 50 to 100 microgram/day, were given to women in 21-day cycles; baboons and beagle dogs received 1 and 4 microgram/kg/day in a similar regimen. After a number of such cycles, megestrol acetate, norethindrone acetate, or dl-norgestrel was given concomitantly. Protein, cholesterol, triglyceride, and phospholipid levels were determined in total plasma and in ultracentrifugally separated lipoprotein fractions. Over the dosage range studied, the effects of the two kinds of estrogen were indistinguishable. Except for human total plasma triglyceride, no dose-related differences were observed. The lowering of serum protein and the increase in cholesterol induced by estrogen were more pronounced in baboons and beagles than in human subjects. The cholesterol-depressing effect of progestational compounds observed in humans was very pronounced in baboons but absent in beagles. In all three species, estrogen increased the lipoprotein fraction cholesterol, except for human low-density lipoprotein cholesterol, which was decreased. Human plasma triglyceride and phospholipid increased on estrogen administration and were decreased by the progestins; in the two animal species, triglyceride is normally very low and the estrogen-induced changes were negligible; the phospholipid rose with estrogen but was unaffected by progestins. In sum, the two animal species show many similarities to, as well as important differences from, the human response of plasma lipids to various contraceptive steroids.

Comparative studies of the Ethynyl Estrogens used in Oral Contraceptives. VII. Effects with and without Progestational Agents on Ultracentrifugally Fractionated Plasma Lipoproteins in Humans, Baboons, and Beagles *

Ethynyestradiol and mestranol, in doses ranging from 50 to 100μg/day, were given to women in 21-day cycles; baboons and beagle dogs received 1 and 4μg/kg/day in a similar regimen. After a number of such cycles, megestrol acetate, norethindrone acetate, or dl-norgestrel was given concomitantly. Protein, cholesterol, triglyceride, and phospholipid levels were determined in total plasma and in ultracentrifugally separated lipoprotein fractions. Over the dosage range studied, the effects of the two kinds of estrogen were indistinguishable. Except for human total plasma triglyceride, no dose-related differences were observed. The lowering of serum protein and the increase in cholesterol induced by estrogen were more pronounced in baboons and beagles than in human subjects. The cholesterol-depressing effect of progestational compounds observed in humans was very pronounced in baboons but absent in beagles. In all three species, estrogen increased the lipoprotein fraction cholesterol, except for human low-density lipoprotein cholesterol, which was decreased. Human plasma triglyceride and phospholipid increased on estrogen administration and were decreased by the progestins; in the two animal species, triglyceride is normally very low and the estrogen-induced changes were negligible; the phospholipid rose with estrogen but was unaffected by progestins. In sum, the two animal species show many similarities to, as well as important differences from, the human response of plasma lipids to various contraceptive steroids.

Radioimmunoassay of unconjugated plasma ethynylestradiol in women given a single oral dose of ethynylestradiol or mestranol

A method for the radioimmunoassay of ethynylestradiol in plasma is described. The sensitivity is 18 pg/ml, recovery 86.5%, and precision 10.9% (coefficient of variation). Normal women, five at each dose level, were given 50 or 80 mug ethynylestradiol or 50, 80, or 100 mug mestranol of uniform bioavailability. Peak plasma levels were consistently obtained in the 1-hour plasma sample with the former compound. With mestranol, the peak levels of ethynylestradiol were lower than with the same quantity of ethynylestradiol and the time-curve of plasma levels much more variable. With this procedure, it is now possible to study certain aspects of the pharmacokinetics of these clinically important compounds.

Comparative studies of the ethynyl estrogens used in oral contraceptives: II. Antiovulatory potency

The occurrence or inhibition or ovulation was inferred from the plasma progestin level measured in the last week of 430 control cycles and of 4,638 cycles from fertile women receiving various antiovulatory steroids, singly and in combination. The substances tested included: mestranol and ethynylestradiol (EE) of homogeneous bioavailability, used alone in a range from 50 to 100 mug per day; these same dose levels combined with various progestins; and finally various proprietary combination and sequential low-dose regimens undergoing clincial trials. Statistical analysis showed ethynylestradiol and mestranol alone to be equipotent over the tested range, although at 50 mug per day superiority of mestranol over EE was suggested. Two preparations of EE at 50 mug per day, one of them a sequential with dimethisterone, showed different potency. At 50 mug per day no estrogen, alone or with a sequential progestin, reached a satisfactory level of effectiveness. However, very small amount in the range of 20 to 40 mug per day were highly effective when combined with quantities of various 19-nor progestins which by themselves are well below the antiovulatory level. This indicated that a synergism exists between these two classes of compounds insofar as their antiovulatory effect is concerned, thus explaining the high contraceptive effectiveness observed with very-low-dose combination regimens.

Evaluation of the clinical performance of three triphasic oral contraceptives: a multicenter randomized comparative trial.

Three hundred thirteen women participated in an open, multicenter comparison of the incidence of intermenstrual bleeding (breakthrough bleeding and or spotting) associated with the use of three triphasic oral contraceptives. Triphasil (n = 107), containing levonorgestrel and ethinyl estradiol, and Ortho-Novum 7/7/7 (n = 97) and Tri-Norinyl (n = 109), both of which contain norethindrone and ethinyl estradiol, were administered over four cycles for a total of 1141 cycles. The total incidence of intermenstrual bleeding was significantly lower with Triphasil (17.2%) than with Ortho-Novum 7/7/7 (39.5%) or Tri-Norinyl (49.0%). The pattern remained the same when findings were analyzed cycle by cycle and for breakthrough bleeding and spotting separately. The incidence of other side effects was comparable for all regimens. Results of this study demonstrate superior cycle control with Triphasil compared with Ortho-Novum 7/7/7 and Tri-Norinyl during the first four cycles of use.

Comparative Studies of the Ethynyl Estrogens used in Oral Contraceptives. VI. Effects with and without Progestational Agents on Carbohydrate Metabolism in Humans, Baboons, and Beagles *

Human subjects, baboons, and beagles were given cyclic regimens of ethynylestradiol or mestranol; after a number of such cycles, concurrent administration of norethindrone acetate, dl-norgestrel, or megestrol acetate was introduced for a similar number of cycles. Carbohydrate tolerance was evaluated by oral glucose tolerance testing in the human subjects and by intravenous glucose tolerance testing in the baboons and beagles. In the human subjects, neither mestranol nor ethynylestradiol at daily doses of 50 to 100 microgram/day produced any effect on fasting glucose levels or on glucose tolerance even after six cycles of treatment. The addition of the progestational compounds also had no effect on these two variables. In baboons, ethynylestradiol and mestranol were bioequivalent and produced a dose-related decrease in the glucose disposal rate. All three progestational agents counteracted this effect in a comparable manner. In beagles, on the other hand, estrogens produced an increase in the glucose disposal rate, and the addition of progestational agents produced an initial fall and a subsequent return to pretreatment levels.

Comparative studies of the ethynyl estrogens used in oral contraceptives: effects with and without progestational agents on plasma androstenedione testosterone and testosterone binding in humans baboons and beagles.

The effects of ethynylestradiol or mestranol given in cyclic fashion, with and without a progestational compound (norethindrone acetate, dl-norgestrel, or megestrol acetate), on plasma androgens and their binding were examined in adult women, female baboons, and beagles. The two estrogens are equivalent in their effect, and there were essentially no dose-related differences over the range examined. In human subjects, the estrogens increased total testosterone and testosterone binding, and decreased free testosterone. In baboons, estrogen produced a transient decrease in total testosterone and an increase in binding. The levels of progestational agents used did not affect total testosterone in humans, as is commonly observed with commercial agents, but did decrease it in baboons. Percentage binding was decreased in both species by the 19-nor compounds, but not by megestrol. Androstenedione levels were unaffected in human subjects, but effects of both estrogens and progestins were seen in baboons. Because of the very low levels of androgens in female beagles, this species did not lend itself well to a study of this kind. However, an increase in testosterone binding was induced by estrogen even in the absence of testosterone/estrogen-binding globulin.

Comparative Studies of the Ethynyl Estrogens Used in Oral Contraceptives: Effects with and without Progestational Agents on Plasma Cortisol and Cortisol Binding in Humans, Baboons, and Beagles *

Ethynylestradiol and mestranol, in doses ranging from 50 to 100μg/day, were given to women in 21-day cycles; baboons and beagle dogs received 1 and 4μg/kg/day in a similar regimen. After a number of such cycles, megestrol acetate, norethindrone acetate, or dl-norgestrel was given concomitantly. Plasma cortisol and percentage binding of cortisol were determined, and the level of free cortisol was calculated. Over this dosage range the effect of the two kinds of estrogen was indistinguishable. In women, 100μg/day produced slightly higher levels of total plasma cortisol than 50μg/day, but no other dose-related differences were seen in any of the three species. Estrogen caused a rise in total cortisol (implying an increased synthesis of transcortin by the liver) in humans and baboons; in the beagle, total cortisol fell transiently. In all three species, the percentage binding of cortisol increased during estrogen administration. There was a very slight, statistically demonstrable increase in total and free cortisol levels in humans and baboon, none in dogs. Of the three progestational compounds, norethindrone acetate and norgestrel produced a slight decrease in total cortisol, whereas megestrol had no effect in humans. The free cortisol was unaltered by these compounds. In both the baboon and the dog, the response was complex, and different from that seen in human subjects. The dog appears to be an inappropriate surrogate for man in the study of these hormonal effects. The validity of the baboon with respect to this progestin-induced effect requires further study; however, its response to estrogens is similar to that of man.

Clinical effects of ethynyl estrogens, used with and without progestational agents, on bleeding patterns, weight, and blood pressure

184 normal volunteers were treated with estrogen (ethynyl estradiol at .05 or .08 mg./day, or mestranol at .05, .08, or 0.1 mg/day) for 6 consecutive cycles. 1677 treatment cycles were accumulated and compared with 342 cycles from a group of 30 IUD users. There were significant differences in cycle regularity (onset of withdrawal bleeding or amenorrhea) between the 2 estrogens, the differences being dose-dependent and changing with successive cycles. The difference was attributed mainly to the frequency of amenorrhea, which was disproportionately high in the early mestranol cycles. Duration of withdrawal bleeding was greater with earlier mestranol cycles. Concomitant administration of a progestin markedly reduced the differences. Variability of cycle lengths was consistently less with mestranol combinations. One estrogen was not consistently better over the other. Cyclic estrogen therapy at any dose did not significantly affect body weight (over a 6-month period) nor systolic and diastolic blood pressure.