Armando de la Pena

Plasma levels and pharmacokinetics of ethynyl estrogens in various populations

A study to determine the pharmacokinetics of single doses of ethynylestradiol (EE) of 35-100 ug administered to a total of 98 women in the United States, Thailand, Nigeria, Sri Lanka, and Singapore. After EE ingestion, plasma samples were collected at various intervals with 65% of U.S. patients exhibiting peak plasma EE levels between 60-90 minutes, and 2/3 showed detectable EE levels at 24 hours using 50-80 ug doses. To assess within-subject variation and range of variation between individuals, subjects in Palo Alto using 35 ug doses were tested twice showing a variation within subjects of 51.8% and between subjects was 119%. In Tucson, subjects using 100 ug EE doses showed a within-subject variation of 13.5% and between subjects was 37%. Absorption phase half-life ranged from 14-22 minutes, distribution phase varied from 1-3 hours, and the elimination half life ranged from 6-14 hours. Nigeria indicated the lowest plasma EE levels while Thailand had the highest levels even when body surface differences were accounted for. Dietary differences may cause differences in drug absorption; in addition, differences in relative muscle/fat ratios could effect storage and metabolism.

Plasma estrogen, progestin, and luteinizing hormone during the normal menstrual cycle in the baboon: Role of luteinizing hormone

Plasma levels of estrogen, progestin, and LH were determined in 10 female baboons throughout the menstrual cycle and in five baboons during the midcycle. The peak in plasma estrogen occurred either on the day prior to the plasma LH peak in three of the 10 cycles, on the day of LH peak in six cycles, or on the day after LH peak in one cycle studied. During the luteal phase, no plasma peak of estrogen was observed. The plasma level of progestin was low in the follicular phase; it rose significantly on the day of or the day after the plasma peak of estrogen. It developed a small peak and then, after an abrupt drop, reached a plateau 5 to 6 dvels at midcycle was usually observed on the day following the LH peak. Three significant rises in plasma level of LH were observed: at the onset of menstruation, just before, and after ovulation. This observation suggests that LH may play an important part in initiating follicular maturation, ovulation, and luteinization during the normal menstrual cycle in the baboon.

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.

Plasma levels and pharmacokinetics of ethynyl estrogens in various populations: II. Mestranol☆

Abstract A total of 89 adult women from Nigeria, Singapore, Sri Lanka, Thailand and the USA were given single oral doses of mestranol ranging from 50 to 100 μg; the subsequent plasma levels of free mestranol and ethynylestradiol were determined by radioimmunoassay, and certain pharmacokinetic parameters calculated. Mestranol is absorbed very rapidly from the digestive tract and maximum plasma levels are attained in 1–4 hours, the majority at 1–2 hours. Detectable levels of mestranol are present 24 hours postingestion in 58% of subjects after a 50 μg dose and in 79% after a 100 μg dose. At all dose levels, highest plasma mestranol levels and area under the curve of plasma levels (AUC) occurred in Sri Lankan women, and lowest plasma levels in Nigerian women, even when corrected for body surface differences. Plasma levels of ethynylestradiol derived from mestranol rose earlier and reached higher values than those of mestranol itself in every locality. The plasma levels of ethynylestradiol derived from mestranol were lowest and total body clearance highest in the Nigerian group at all dose levels; total body clearance was similar in the other localities. The AUC of plasma levels of ethynylestradiol was compared, by locality, on a dose-for-dose basis for the administration of mestranol or of ethynylestradiol itself. There was no significant difference between the two drugs, except at one dosage level in Thailand. These findings suggest that ethynylestradiol and mestranol are similar in terms of AUC ; a higher peak and a faster decline are observed after administration of the former compound. Substantial differences between localities in the clearance rates of mestranol are suggested; whether these are due to differences in distribution or rate of metabolism or to differences in absorption remains to be determined.

Radioimmunoassay of plasma androstenedione, testosterone and 11β-hydroxy androstenedione after chromatography on Lipidex-5000 (Hydroxyalkoxypropyl sephadex)

Abstract 11β-Hydroxy androstenedione is a C29-steroid almost exclusively of endogenous adrenal origin. It represents a major pathway of biological inactivation of adrenal androstenedione, an important androgen precursor. If the proportion of biosynthesized adrenal androstenedione that becomes 11β-hydroxylated were constant, measurement of this product could serve as an indicator of the contribution of the adrenal to overall androstenedione production. For these reasons a procedure for the isolation of testosterone, androstenedione, and 11β-hydroxyandrostenedione by chromatography on Lipidex-5000, followed by radioimmunoassay measurement, has been developed and the analytical characteristics of the procedure evaluated.

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.

Antisera for radioimmunoassay of 17α-ethynylestradiol and mestranol

Antisera for radioimmunoassay of 17alpha-ethynyl estradiol and mestr anol were prepared and tested. The antisera were prepared by immunizing rabbits with 6(O-carboxymethyl) oxime-bovine serum conjugates from 6-oxo-17alpha-ethnyl estradiol and 6-oxomestranol. Antisera raised to 17alpha-ethynyl estradiol by employing steroid-protein conjugates coupled at either carbon-6 or -7 proved to be highly specific and showed little cross-reaction with mestranol. Antisera for mestranol also showed little cross-reactivity while the antibody to the 6-linked agent showed only moderate cross-reaction to 6-hydroxymestranol but an avidity for the 6-oxomestranol which exceeded that of the reference compound. This assay has been employed in measuring these substances after ingestion of oral contraceptives.

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.