Research activities in the field of oral contraceptives in the People's Republic of China.

Abstract

A review of Chinese research initiated since 1963 on oral contraceptives (OCs) long-acting OCs the injectables and progestogen-releasing vaginal rings is presented. Clinical trials carried out since 1963 on full dose half-dose and quarter-dose norethisterone compound (pill No. 1) and megestrol compound (pill no. 2) in 1965-1969 followed by an 8th-dose of norethisterone in 1976 showed that a decrease in dosage would not reduce the contraceptive efficacy. Research on a monthly oral contraceptive containing quinestrol and various progestogens began in 1967. In 43373 women using the monthly pill in 347178 cycles in 1969-76 contraceptive efficacy was 98.3%/woman-year. With a lower dose pill contraceptive efficacy was 95.67%/woman-year in a study of 10783 women totalling 130020 cycles during 1975-79 but the incidence of side effects was markedly reduced. Progestin No. 1 a new synthetic progestin from megestrol acetate had a significant anti-implantation effect if used before ovulation. Since 1970 9 kinds of visiting pills have been developed for couples who are separated most of the time and see one another only for vacations. These include megestrol-quingestanol chlomadinone-quingestanol and norgestrienone and provide 98% protection with few side effects. A new combined injectable megestrol acetate is an improvement on combined megestrol acetate achieved by replacing the estradiol 17-beta-cyclopentyl propionate by 17-beta-estradiol. In a clinical trial of norethisterone enanthate including 2532 subjects totalling 27816 cycles the contraceptive efficacy rate was 99.9% with few menstrual changes. In a clinical trial of the vaginal ring performed in Shanghai since 1975 contraceptive efficacy among the 2470 users was 97.85%.