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Activities of the Special Program of Research, Training and Development in Human Reproduction, World Health Organization in the field of long acting contraceptives.
In: Bangladesh Fertility Research Program. Workshop on Injectable Contraceptives: Noristerat, Dacca, Bangladesh, April 25, 1980. [Dacca, Bangladesh, BFRP, 1980]. 70-80.Following a brief introduction to the World Health Organization (WHO) Special Program of Research, Development and Research Training in Human Reproduction, established in 1972, focus is on what has been achieved thus far with long-acting injectable fertility regulating agents based on steroidal hormones and possessing a duration of action of at least 1 month. Over the last 20-year period, several estrogen-progestin combinations have been developed as monthly injectable contraceptives. The Special Program has initiated a series of clinical pharmacological studies aimed at developing new and improved estrogen progestin injectable formulations. 1 preparation, composed of norethisterone enanthate (50 mg) plus 5 mg of estradiol valerate, has shown promise in preliminary clinical studies. 3 progestogen only preparations with a duration of action of several months have been tested clinically: clormadinone acetate, depo-medroxyprogesterone acetate and norethisterone-enanthate. The 1st clinical trials utilizing the heptanoic acid ester of norethisterone raised considerable hopes, for no pregnancies were observed in 70 highly fertile women given the drug every 90 days. In a WHO trial preliminary data on Depo-Provera (DMPA) bleeding irregularities were responsible for the discontinuation of 9.3 subjects/100 women-years; prolonged amenorrhea accounted for the termination of 11.5 subjects/100 women years. There are several ongoing studies to evaluate the effects of the injectables on users. Norethisterone enanthate, although not possessing the same degree of effectiveness as DMPA, when adminstered every 3 months, remains an attractive injectable because of its lower incidence of amenorrhea.
Multinational comparative clinical evaluation of two long-acting injectable contraceptive steroids: norethisterone oenanthate and medroxyprogesterone acetate. 1. Use-effectiveness.
Contraception. 1977 May; 15(5):513-533.A 10-center study of the use-effectiveness of long-acting systemic contraceptive agents is reported. 200 mg of norethisterone enanthate (NET-EN) was administered every 12 weeks + or -5 days to 832 women and 150 mg of depot medroxyprogesterone acetate (DMPA) was administered to 846 women on the same schedule. The cumulative 12-month gross pregnancy rate/100 woman-years was 3.6 + or -.7 for NET-EN and .7 + or -.4 for DMRA. 54% of all the pregnancies in the NET-EN group was contributed by 2 of the 10 centers. 75% of the NET-EN pregnancies occurred during the 1st injection period, primarily in the last 4 years. The admission weight of NET-EN women who became pregnant was significantly lower than those for whom the method was successful. This difference was absent in the DMPA group. The cumulative discontinuation rate for medical reasons at 12 months was 16.9 + or -1.4/100 woman-years for NET-EN and 23.4 + or -1.7 for DMPA. The discontinuation rate for amenorrhea was significantly higher for DMPA than for NET-EN. Differences between the drugs for bleeding irregularities were insignificant as were discontinuations for nonmedical reasons. This study represents a successful attempt at comparing the use-effectiveness of 2 drugs under highly standardized conditions using a large sample drawn from a number of internationally representative settings.
In: Diczfalusy, E., ed. Regulation of human fertility. (Proceedings of the WHO Symposium on Advances in Fertility Regulation, Moscow, USSR, November 16-19, 1976) Copenhagan, Denmark, Scriptor, 1977. p. 323-360Long-acting systemic contraceptives inhibit fertility either at a central or peripheral level. In some instances, a mixed reaction is likely to be working: during the 1st portion of the drug's life-span the contraceptive effect is exerted at a hypothalamic central level, whereas later on--when ovulation is restored--the action is on the cervix or uterus. The most important factor holding back utilization of long-acting agents is serious interference with regularity of the menstrual cycle, and delivery systems must be devised with zero-order release rates to improve cycle control and acceptability. Monthly injectables consisting of synthetic progestins alone proved unsuitable for contraception because of frequent and prolonged amenorrhea. Addition of an estrogenic substance helped cycle control, and a dihydroxyprogesterone acetophenide plus estradiol enanthate combination seems most worthy of clinical investigation; so far, 15,000 woman-months of experience have yielded no unwanted pregnancies. Few bleeding pattern irregularities were reported, but premenstrual tension, dysmenorrhea, and libido changes occurred. Reversibility of drug-induced anovulation has been shown by spontaneous ovulation resumption 12-42 weeks after cessation. Tri-monthly injections of Depo Provera resulted in pregnancy rates averaging .5/100 woman-years of use. Biannual injectable and sustained release systems are discussed and data are presented.