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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.
A preliminary pharmacokinetic and pharmacodynamic evaluation of depot-medroxyprogesterone acetate and norethisterone oenanthate.
Fertility and Sterility. 1980 Aug; 34(2):131-9.2 populations attending WHO centers, one in Sweden and one in India, participated in a comparative, pilot trial of 2 increasingly popular injectable progestin-only female contraceptives, Depo-Provera and Norigest. The purpose of the study was to assess the pharmacokinetic and pharmacodynamic properties of the 2 formulations (depot medroxyprogesterone acetate and norethisterone enanthate). Differences were found between Swedish women and Indian women in their reactions to the 2 drugs: 1) Norigest was detectable in blood samples a significantly shorter time after injection of the agent in Indian women than in Swedish women; this difference was not apparent with Depo-Provera. 2) Although there was no difference at the 2 centers in the time of ovulation return for subjects receiving Norigest, 0 of 4 Swedish women ovulated more than 156 days after Depo-Provera injection, whereas all 4 Indian women ovulated within 73 days of Depo-Provera injection; in the Swedish women, the levels of medroxyprogesterone were undetectable at time of return to ovulation, whereas Indian women had levels of .6 ng/ml when ovulation resumed. 3) In both cultures, Depo-Provera users had significantly more episodes of bleeding and spotting than Norigest users. This preliminary report emphasizes the variety of responses possible to injection of different contraceptive progestins among various populations and points to the need for further culturally comparative studies.