On the mechanism of action of progestins.
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A clinical trial was carried out in which Norigest (200 mg norethisterone oenanthate) was administered by intramuscular injection every 56 days into 383 women studied for 5,521 woman-months of use. No pregnancies occurred. Continuation rates at the end of one, two and three years were 76.6%, 63.7% and 33.8%. Only minor side-effects were recorded. After one year of use, 20.1% women had gained more than 2 kg in weight and 14.8% had lost more than 2 kg. There was marked disruption of the menstrual pattern and irregular bleeding was the major cause of discontinuation. In 38% of the injection intervals analysed, women were amenorrhoeic. Norigest proved an effective and acceptable method of fertility control.
Intravenous glucose tolerance tests, and estimations of prothrombin time, and plasma coagulation factors VII and X, were made on 12 women receiving 200 mg norethisterone oenanthate intramuscularly as a contraceptive. These estimations were made before, and at 2 and 12 weeks after, a single injection of norehisterone oenanthate. There was no significant effect on the intravenous glucose tolerance, prothrombin time, or on plasma coagulation factors VII and X, further confirming the safety of norehisterone oenanthate when used as a short-term injectable contraceptive.
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Studies of the pharmacokinetics of three contraceptive steroids, ethynyloestradiol, norethisterone and norethisterone oenanthate, in large groups of women are reviewed. Extremely wide variations were observed between women in the various calculated pharmacokinetic parameters. Studies carried out in small groups of subjects may give misleading results. It is difficult to ascribe any meaning and interpretation to most of the derived values but they do provide a means of comparing aspects of the metabolism of the various steroids. It is difficult to relate the pharmacokinetic values to the various biological actions of the steroids. However, the wide variations between subjects in the pharmacokinetic parameters must indicate equally wide variations in the biological activity of the steroids. Subjects in whom the bio-availability is low or where the rate of metabolism is rapid might be expected to respond differently, both in terms of efficacy and side-effects, from subjects with high values for bio-availability and a slow metabolism.
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Subcutaneous injection of single doses (5 to 20 mg/kg) of DMPA or NE in virgin female rats caused reduction in number and diameter of CL, and increase in number of atretic and cystic follicles in the ovary. Histological examination of the endometrium of these animals showed low cubiodal cells with sparse distribution of low columnar cells, glands with atrophic changes and compact uterine stroma with or without patches of oedema. The results suggest regressive and atrophic changes in the ovary and endometrium.
Injectable hormonal preparations can be highly effective and satisfactory contraceptives. The two main preparations available today are depot medroxy progesterone acetate (DMPA) and norethisterone oenanthate (NET-OEN), but several other approaches are currently under clinical trial. Injectable contraceptives have some unique advantages which give them justifiably wide appeal amongst many groups of women. However, they do have a number of disadvantages including invariable menstrual disturbance and a delay in the return of fertility. One formulation of DMPA, Depo-Provera, is probably the most extensively investigated single hormonal contraceptive ever made. These studies indicate that it is remarkably safe and does not face any more unresolved issues than the combined pill, intrauterine device or tubal sterilization. However, for a number of disparate emotional and political reasons it has attracted the attention of several consumer and feminist groups, who have waged a prolonged and quite unjustified campaign against it. It is to be hoped that future debate will be conducted on a more informed, rational and less emotional basis. Injectable contraceptives should have an important place in the family planning armamentarium of all countries, and current developments should lead to a decrease in concerns about presently available agents. This should further increase the widespread acceptability of this approach to contraception.
The effect of long acting progestational contraceptive injection, norethisterone-oenanthate was studied in twenty six women. The post injection results showed a significant decrease in total lipids, free cholesterol, total cholesterol, triglycerides, phospholipids and free fatty acids.
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Serum progesterone (P) and norethisterone (NET) levels following injection of norethisterone enanthate (NETEN) were studied in 11 regularly menstruating women. In 6 subjects 200 mg NETEN was administered to the gluteal (IG) or deltoid (ID) region sequentially. The serum P levels remained anovulatory (less than 4 ng/mL) up to 12 weeks. Serum NET levels were similar whether injection was given IG or ID (paired t - test, NS). In 5 subjects given a 150-mg dose, serum P levels remained anovulatory up to 11 weeks. Serum NET levels declined faster than with the 200-mg dose, but the difference was not significant (Student's t - test, NS). Wide inter-subject variations were seen in both groups. NETEN therefore can effectively be administered in gluteal or deltoid regions. A lower dose of 150 mg may have contraceptive potential on an 8-week schedule.
Injectable progestogen, norethisterone enanthate (NET-EN, 200 mg/ml) was administered to 122 women at 2 month intervals for more than 1 year. Only a minority of women had consistently normal cycles. Most women experienced some menstrual irregularities: 57% of users experienced irregular bleeding, 32% developed amenorrhea, while only 11% showed regular cyclic bleeding. Important nonmenstrual side effects were weakness and abdominal pain. No appreciable changes in body weight and blood pressure were recorded.
To test the efficacy and tolerance of progestagens as contraceptives in systemic lupus erythematosus (SLE), 200 mg IM norethisterone enanthate was administered to 10 patients, 0.03 mg/day oral levonorgestrel to 15 patients and they were compared with 18 control patients. There were 4 episodes of active SLE in 48 patient-months on norethisterone enantate and 6 episodes in 122 patient-months on levonorgestrel as compared with 9 episodes of active disease in 298 control patient-months (p = ns). There were no pregnancies and intermenstrual bleeding led to discontinuation of medication in 30% of patients. Progestagens may be an alternative contraceptive method in SLE.
Endometrial bleeding and alteration in blood coagulation, fibrinolysis, ovarian function and endometrial morphology were studied in twelve normally menstruating women who received the injectable contraceptive norethisterone enanthate (NET-EN) 200mg at 60-day intervals. Levels of clotting factor VII declined significantly during episodes of irregular bleeding compared to those during both normal pretreatment menstruation and the bleeding-free period during treatment. Antithrombin III and fibrinolytic activity, expressed by euglobulin lysis time, showed no marked change. The average level of progesterone during the bleeding-free period was slightly but significantly lower than that during the bleeding period. There were no significant alterations in the mean levels of estradiol and the ratio of estradiol to progesterone. The endometrial biopsies showed considerable individual variation and seem to be independent of the effects of NET-EN on ovarian function.