Clinical experience with Microlut.
D-Norgestrel (Microlut; code name SH 9.0999C) in daily dosages of 30 mcg was studied. D-norgestrel is a synthetic progestogen with a natural steroid configuration. Only the d- component of dl-norgestrel is biologically active. Results were evaluated from 15,939 menstrual cycles of 1969 women using this preparation. Subsequently, more than 3200 cycles have been studied and results do not alter those reported here. Treatment lasted 6 months in 1459 women, 12 months in 740, and 18 months in 132 women. 91% of the women were between 21 and 40 years of age. 83% were Mestizas and 11% Caucasian. Their fertility was very high. More than half had been pregnant 3-6 times and 30% had had 7 or more pregnancies. In all, there were 55 pregnancies during the study with a Pearl rate of 4.14/100 woman-years. However, 43 of these pregnancies were attributed to administration errors, leaving a drug failure rate of .9/100 woman-years. All infants born were normal. 1188 (81%) of the women had regular menstrual cycles before treatment, of whom 70-74% remained eumenorrheic. Breakthrough bleeding was noted in 10% of cycles. Carcinoma was not found in any patient. Body weights were equally increased or decreased. Blood pressures remained the same. Libido increased more frequently than it decreased. Thrombophlebitis occurred in 4 cases during the 1st year of treatment, none later. The same frequency was reported before treatment. Other side effects, except nausea, were not frequent or serious. Studies of plasma luteinizing hormone and follicle stimulating hormone levels revealed distinct peaks in the middle of the last untreated cycles. During treatment, these peaks were the same as in controls. It was thought that ovulation was not inhibited but that the corpus luteum function was altered. The endometrial changes that were found are thought to explain the menstrual disorders and also the contraceptive action. Cervical mucus changes seemed to interfere with the ability of the sperm to penet rate. Vaginal cytology was observed to be altered. Insular levels and oral glucose tolerance tests were normal. Liver function tests showed only minor abnormalities. Thyroid, kidney, and adrenal functions remained normal. Serum electrolytes and serum metals were unchanged, except copper which was reduced. Microlut is considered contraindicated in patients with acute or chronic liver disorders, in those with Dubin-Johnson or Rotor syndromes, or for those with a history of jaundice during pregnancy. Microlut is suitable for widespread use as an effective oral contraceptive.