Contraception with megestrol acetate implants. Megestrol acetate levels in plasma and the influence on the ovarian function

Effect of nomegestrol acetate, a new 19-nor-progesterone derivative, on pituitary-ovarian function in women

After two control cycles, 13 normally menstruating women were treated from day 5 to 25 of the third consecutive cycle with nomegestrol acetate (NOM Ac) 1.25, 2.5 or 5 mg once a day. Plasma oestradiol, FSH and LH concentrations were assayed daily from day 5 to day 25 and plasma progesterone concentrations from day 12 to day 25. Ovulation was inhibited in every woman; LH and progesterone levels were uniformly depressed. With 5 and 2.5 mg/day, plasma oestradiol remained low with high FSH values. With 1.25 mg/day, oestradiol concentrations reached levels similar to those achieved during the control follicular phase, with a concomitant decrease in FSH secretion. These results show an hypothalamic-pituitary effect and suggest an ovarian action, both responsible for a potentially useful contraceptive property.

Ovarian function, bleeding control and serum lipoproteins in women using contraceptive vaginal rings releasing five different progestins

Ovarian function, bleeding patterns and serum lipoproteins were studied in women using contraceptive vaginal rings (CVRs) of dimethyl-polysiloxane impregnated with steroids. The different CVRs were used for about 10 cycles each. The following groups were studied, with the daily steroid dosage given in parentheses. Women using CVRs delivering levonorgestrel (290 micrograms), norethisterone (850 micrograms), medroxyprogesterone acetate (700 micrograms) or megestrol acetate (1.9 mg), all of which were in combination with estradiol (200 ug). Women using CVRs delivering progesterone (5.2 mg). Women taking megestrol acetate orally (15 mg/day) for three weeks. In all women except those using the levonorgestrel CVR, there were indications of incomplete suppression of ovarian activity as shown by elevated levels of progesterone and/or estradiol peaks. Bleeding control seemed to be good with the levonorgestrel CVR and rather poor with the others. Levonorgestrel treatment was associated with a decrease in high density lipoprotein cholesterol (32%) and triglycerides (25%) and a 16% decrease in apolipoprotein A-I. Norethisterone induced a 10% decrease in A-I and a reduction of cholesterol in very low density lipoprotein. All other lipid and apolipoprotein B, A-I and A-II values were unaltered with the administration of the CVRs and with oral megestrol acetate. Levonorgestrel was given in a higher dose than the other progestins, but the absence of effects of the high oral dose of megestrol acetate on the serum lipoproteins indicates that the progesterone-derived progestins in adequate doses probably would not alter the lipoprotein metabolism. Higher doses of progestins are needed to achieve acceptable control of ovarian activity and bleeding patterns than seen with these CVRs.

Pituitary and ovarian function during contraception with one subcutaneous implant releasing a progestin, ST-1435

Three women received one subcutaneous SilasticR capsule containing 40 mg of ST-1435 for contraception. Plasma levels of ST-1435, a 19-norprogesterone derivative, were measured during the treatment period of 13-15 months. The effects of treatment on pituitary and ovarian function were determined by assaying plasma concentrations of LH, FSH, estradiol and progesterone. The mean concentrations of ST-1435 during the treatment varied from 52 to 220 pg/ml in different subjects. These low concentrations of progestin were sufficient to suppress ovulation and make the implant effective for more than one year. No mid-cycle gonadotropin peaks were observed during the treatment. The subjects showed constantly low estradiol levels, thus also indicating a suppression of follicle development. Regular cyclic activity of the pituitary and ovaries, without the occurrence of ovulation, was observed in one subject. Increasing levels of estradiol parallelled a decrease of FSH and LH. It therefore seems that the negative feedback action of estradiol on gonadotropin release is unaffected but the positive feedback action of estradiol on LH appears to be blocked by the progestin ST-1435.

Fluid-filled silastic capsules : a new approach to a more constant steroidal drug delivery system

A new approach to a more constant steroid delivery system was made in which 7,9 mg of norethisterone acetate was shaped into a cylindrical pellet (diameter 1.47 mm, length 4 mm) and placed inside a silastic capsule (i.d. 1.57 mm, o.d. 3.18 mm) of 5 mm effective length. The extra space available around the pellet was filled with physiological saline. For the sake of comparison, the same amount of crystalline norethisterone acetate was packed up to 5 mm length inside a silastic capsule of the same dimensions. The incorporation of fluid (saline) in the system not only caused a marked decrease in the initial high release but also a more constant release. Varying the pellet diameter showed that release of the steroid increases with the increase in surface area of the pellet.

Contraception with subcutaneous capsules containing ST-1435. Pituitary and ovarian function and plasma levels of ST-1435

An RIA for a new progestin, ST-1435, was developed. Plasma concentrations of this steroid were measured in three women having three subcutaneous capsules, each containing 40 mg of ST-1435. Pituitary and ovarian functions were assessed by measuring plasma levels of LH, FSH, estradiol and progesterone. Plasma profiles of ST-1435 were characterized by high and irregular peaks all the way through the study period of 7-9 months. Concentrations below 100 pg/ml were not observed, whereas the highest peaks reached concentrations of 10.1 ng/ml. Plasma estradiol concentrations remained uniformly suppressed below 100 pg/ml, thus indicating a suppression in follicle development. As judged by constantly suppressed progesterone concentrations, no ovulations occurred during the treatment. Plasma FSH concentrations remained at the upper limit of the follicular phase, and those of LH at the lower limit of the luteal phase of the normal menstrual cycle. No midcycle gonadotropin peaks were observed.

Subdermal norethindrone pellets -- a method for contraception?

The mode of action of compressed pellets containing 85 per cent norethindrone (NET) and 15 per cent cholesterol was studied. Four pellets were inserted subcutaneously, in each of five healthy volunteers and left in place for 200--229 days. The NET content of the pellets varied between 23.9 mg and 25.6 mg; and the cholesterol content between 4.2 mg and 4.5 mg. Plasma levels of NET, estradiol and progesterone were determined by radioimmunoassays. Plasma levels of NET varied mostly between 1--2 ng/ml the first month after insertion. After two months plasma levels of NET ranged between 0.5 ng/ml and 1 ng/ml in all volunteers and there was a gradual decrease of the plasma NET levels throughout treatment. Pronounced day-to-day variations in plasma NET levels were recorded. The release rates of NET was calculated to be between 187 micrograms/day and 243 micrograms/day among the five volunteers. Ovulations occurred in four out of five subjects during treatment. This study indicates that the release of gestagen from four NET pellets was only initially high enough to completely inhibit ovulation and that to accomplish full contraceptive efficacy, a higher dose, i.e. more pellets, would have to be inserted.

Plasma levels of norethindrone and effect upon ovarian function during treatment with silastic implants containing norethindrone

The study was made to evaluate the effect upon the ovarian steroid pattern during treatment with subcutaneously implanted silastic rods containing norethindrone. Four rods, each containing 37 mg norethindrone (NET), were implanted subcutaneously in five women and left in place for 135--200 days. Plasma levels of NET, estradiol and progesterone were determined by radioimmunoassays. After an initial peak found in all subjects, the plasma level of NET declined. Great day-to-day variations of NET were found. Ovulations were suppressed during treatment in three subjects. One subject had regular ovulations throughout treatment and in one subject a single ovulation was recorded. Peaks of estradiol without subsequent ovulation were found in two subjects. The bleeding pattern was irregular; three subjects had varying degrees of spotting and bleeding, two subjects were amenorrheic. The average daily release rate was 300/micrograms, calculated from the amount of steroids lost from the removed rods. This study indicates that the release of steroid from four NET rods is high enough only initially to completely inhibit ovulation.

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.