Serum levels of d-norgestrel, luteinizing hormone, follicle-stimulating hormone, estradiol, and progesterone in women during and following ingestion of combination oral contraceptives containing dl-norgestrel

Three formulations of dl-norgestrel were administered daily to groups of three women for five consecutive days. The serum levels of d-norgestrel were related to the dosage of dl-norgestrel ingested. Peak concentrations in the circulation of synthetic gestagen were attained a half hour to three hours after oral administration, followed by a rapid and sharp decline in levels until the next dose. Three women received 500 micrograms of dl-norgestrel and 50 micrograms of ethinyl estradiol for 21 days followed by six to seven days of no medication for two consecutive cycles. The gonadotropins remained suppressed for four to six days when therapy was discontinued. The daily concentrations of estradiol varied from less than 5 to 81 pg. per milliliter, and there was no difference in estrogen values during the nontreatment and treatment days. Due to the long half life of norgestrel, the one-week pill-free interval is not long enough for the complete recovery of the reproductive axis from the inhibition of oral contraceptives.

d-Norgestrel concentrations in maternal plasma, milk, and child plasma during administration of oral contraceptives to nursing women

In order to correlate plasma and milk concentrations of d-norgestrel (d-Ng) in lactating women, three oral contraceptives, containing different amounts of this synthetic gestagen, were given to 15 fully lactating women, starting two months post partum. Plasma and milk samples were collected according to a special schedule. d-Ng concentrations in plasma and milk were measured by radioimmunoassay. When d-Ng was measured in milk, extraction was performed with petroleum ether and in the radioimmunoassay an internal standard was used. This method is evaluated in the present paper. The plasma: milk ratio of d-Ng was found to be about 100:15 and the amounts of d-Ng transferred with 600 ml. of milk per day were calculated to be 0.3 an 0.15 microgram with daily intakes of 250 and 150 microgram of d-Ng, respectively, corresponding to about 0.1 per cent of the given dose. When the women received 30 microgram of d-Ng daily, no d-Ng could be detected in the milk. In three of the breast-fed children the d-Ng concentration in plasma was measured. This concentration was found to be in the same range as would be expected after oral d-Ng medication to adults, allowing for body weight differences, indicating that d-Ng is metabolized and is not accumulated in the baby.

The detection and measurement of D-norgestrel in human milk using Sephadex LH 20 chromatography and radioimmunoassay

An accurate sensitive method for the assay of D-norgestrel in human milk is described. The steroid is isolated from an ether extract of milk by Sephadex LH 20 chromatography in the system iso-octane-benzene-methanol (70:20:10 v/v). The radioimmunoassay utilises a specific antibody produced in rabbits against D-'norgestrel 3-(O-carboxymethyl) - oxime coupled to bovine serum albumin with D-norgestrel 3-(0-carboxymethyl) -oxime/ [125I]-iodohistamine conjugate as radioligand. Accuracy, sensitivity and blank value are satisfactory. Milk samples were obtained from three subjects treated with 30 microgram/day D-norgestrel, treatment commencing two weeks following parturition. Significant amounts of D-norgestrel were found, ranging between 92-135 pg/ml milk at the end of the first two-week treatment regimen. In two of three subjects, lower, but significant concentrations (53 pg and 35 pg/ml respectively) of steroid were found at the end of four weeks treatment. In the third subject, D-norgestrel could not be detected at this time. As a check on the specificity of the assay, three samples were submitted to additional chromatographic purification on alumina thin layer in the system benzene-cyclohexane-ethanol (70:27:3 v/v). Although this additional chromatographic step yielded somewhat lower values, agreement between the respective sets of results was good. The significance and implications of these findings are discussed.