Low-dose progestagens as contraceptive agents
Elstein, M.
Ippf Medical Bulletin 4(1): 2-4
1970
ISSN/ISBN: 0019-0357 PMID: 12255089 Document Number: 27369
The low dose progestogens available for use as contraceptive agents are identified, and the evidence of their possible mode of action is discussed. The relative acceptability and clinical effectiveness is also indicated. Progestational agents fall into 2 groups: 17-acetoxy progestogens (chlormadinone acetate 500 mcg and megestrol acetate 500 mcg) and 19-norsteroids (norgestrel, 50-75 mcg, norethisterone acetate, 300 mcg, norethisterone 500 mcg, and ethynodiol diacetate 250-500 mcg). The effect of the progestational agents on the hypothalamo-pituitary-ovarian mechanisms can be interpreted from leutinizing hormones (LH) levels. 17-acetoxy progestogens disturb LH excretion and the dose of these drugs which inhibits ovulation is very close to the dose exerting local contraceptive action. In 19-norsteroids administration, the LH midcycle surge is still present but long-term use may distort the LH peak rather than suppress it. 19-norsteroids seem to effect the ovarian function, although the corpus luteum appears normal. Evidence for an ovarian effect produced with chlormadionone acetate is less convincing. An effect of these progestogens on the endometrium appears to be absent, however, this assertion is without the support of electron microscopy study. Cervical mucus is a major site of action of the 17-acetoxy group although this may be unrelated to contraceptive effectiveness. The data on the effect of 19-norsteroids on cervical mucus is conflicting. Animal studies with low dose progestogens have shown unusual findings to be absent, although breast nodules were found in the beagle. The disadvantages of the low dose progestagens are in the irregular bleeding and the use effectiveness rate of 9/100 woman-years and method failure of 6/100 woman-years.