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PubMed1981

Pharmacokinetics of norethisterone oenanthate in humans.

The pharmacokinetics of a dose of 200 mg NET-OEN were studied after intramuscular injection into nine subjects. Blood levels of NET and NET-OEN increased rapidly, reaching peaks in most subjects within seven days. At all times after injection, serum levels of NET exceeded those of NET-OEN. The half-life of absorption varied from 5.4 to 22.3 days and the half-life of elimination varied from 7.5 to 22.5 days; there was a significant correlation (R = 0.78) between these two half-lives. There were significant correlations between the absorption half-lives and the peak values of NET and NET-OEN, the time to reach peak values and the time for which NET was detectable in serum. In all subjects NET was detectable in the circulation for a longer time after injection (mean value 74 days) than NET-OEN (mean value 43 days). The time for which the two steroids were detectable in the circulation showed a significant correlation with the elimination half-lives but there was no correlation with the peak values attained, the time taken to reach peak values and bioavailability. There was a two-fold variation between the subjects in the bioavailability of NET, less than 5% of the bioavailable NET was released after day 60.

Absorption↗
PubMed1981

Phase I clinical trial of two contraceptive preparations. Norethisterone enanthate (NEN) and norethisterone acetate (NET).

A Phase I Clinical Trial was conducted in 20 fertile Cuban women using for contraception: Norethisterone Enanthate injectable (NEN) and Norethisterone Acetate minipill (NET). Women had daily blood sampling during a control cycle and during the second month of treatment with either drug. Discontinuation rate was very low (1/20). The preovulatory LH and FSH peaks were abolished in all treated women, basal levels remaining unchanged. The incidence of menstrual disorders as amenorrhea, spotting and inter-menstrual bleeding was greater in subjects using NEN than in those on NET. No pregnancy was reported. Blood pressure was unaltered. Renal, hepatic and thyroid function were unchanged. Cholesterol levels were unchanged and triglycerides significantly decreased with both preparations. Women on either NEN or NET underwent OGTT before and after 2 months treatment. In NEN group glycemia was unchanged but insulin levels increased significantly at 120 minutes. In NET group glycemia and insulin levels were significantly increased at all times during post-treatment OGTT. Both forms of Norethisterone were well accepted by this group of women despite menstrual irregularities. Significant changes were found in the group using NET with regard to carbohydrate metabolism.

Blood Glucose↗
PubMed1984

Pharmacokinetics of different doses of norethisterone oenanthate.

Doses of norethisterone oenanthate of 300, 150, 100 and 50 mg were administered to four groups of subjects. Due to wide intersubject variations there were no statistically significant differences in the pharmacokinetic parameters for the different groups but there were significant correlations between the dose and the mean values for these parameters. There was little difference between the groups in the duration for which ovarian function was suppressed due to the inter-subject variation being greater than the inter-dose effect. The duration of the antifertility action of norethisterone oenanthate cannot be increased by increasing the dose above the standard 200 mg; however, with an injection interval of 60 to 70 days, it seems likely that the dose could be reduced to 150 mg.

Adult↗
PubMed1994

Animal toxicity studies performed for risk assessment of the once-a-month injectable contraceptive Mesigyna.

Results from toxicity studies performed for risk assessment of the combined injectable hormonal preparation Mesigyna are reviewed. Both components of Mesigyna, i.e., estradiol valerate (E2Val) and norethisterone enanthate (NET-EN), have been thoroughly investigated as individual compounds and some limited toxicity data have been obtained for the combination. Most findings which were gathered in these studies from different animal species occurred in the gonads, accessory genital and endocrine organs and can be related to the known species-specific pharmacological activity of a typical estrogen or progestin, respectively. No additional or unexpected information which might indicate a possible estrogen/progestin interaction was gained from the administration of the combined preparation to animals. Based on the results from toxicity testing, there were no objections to the long-term therapeutic use of Mesigyna for hormonal contraception. The predictive value of the effects (including the tumorigenicity) observed in the common laboratory animals with regard to human safety is critically discussed, taking the vast amount of previous experience with hormonal contraceptives into consideration. The conclusion is drawn that there is no animal model for safety assessment of sex steroids that adequately represents the human situation. Quantitative extrapolations from animal toxicity findings to humans, therefore, are not possible. Especially, the value of long-term studies and of toxicity studies on estrogen/progestin combinations is put into question. Like endocrine pharmacology studies, the toxicity studies with these steroid hormones are useful for the characterization of the possible endocrine pharmacological profile only.

Animals↗
PubMed1995

A comparative study on the return to ovulation following chronic use of once-a-month injectable contraceptives.

A comparative study was undertaken involving 21 Mexican women who discontinued the use of medroxyprogesterone acetate 25 mg plus oestradiol cypionate 5 mg (Cyclofem) and norethisterone enanthate 50 mg plus oestradiol valerate 5 mg (Mesigyna) to assess the time required for the return to menses and ovulation. All subjects were exposed to once-a-month injectable contraceptives for two years and were followed for 120 days after the last injection. The urinary concentration of oestrone glucuronide and pregnanediol glucuronide was determined daily in all subjects beginning one month after the last injection. The results disclosed that ovulatory cycles were documented after 120 days of the last injection in six women of each studied group. Similar endometrial bleeding patterns were observed in both groups, indicating that the two drugs have alike pharmacokinetic and pharmacodynamic effects.

Adult↗
PubMed1983

Variability of pharmacokinetic parameters for contraceptive steroids.

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.

Biological Availability↗
PubMed1989

Serum progesterone and norethisterone levels following injection of norethisterone enanthate in different sites and doses.

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.

Adult↗
PubMed1977

Effects of long-acting steroid contraceptives on ovarian and uterine histology of rats.

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.

Animals↗
PubMed1982

Long acting injectable hormonal contraceptives.

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.

Animals↗
PubMed1984

The effect of injectable contraceptive on lipid metabolism in women.

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.

Adult↗