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Pharmacodynamic effects of once-a-month combined injectable contraceptives.

Abstract：

:The pharmacology and clinical assessment of existing first generation once-a-month combined injectable contraceptives, mainly Deladroxate and Chinese Injectable No. 1, are reviewed. Although these two types of monthly injectables have been used in some million women in China and Latin America, Deladroxate needs indepth re-evaluation of its long-term toxicity and possible accumulation. For injectable No. 1, its disadvantage of being administered on an erratic schedule will cause significant confusion in family planning practice. When used in a strict once-a-month schedule, it is not sufficiently effective for contraception. In order to attain predictable menstrual cycle control as well as high efficacy with a 30-day injection schedule, two improved once-a-month injectable formulations, Cyclofem and Mesigyna, were developed. Pharmacokinetic/pharmacodynamic study on estrogenic components suggested that estradiol valerate and cypionate were suitable estrogen esters to give elevated plasma estrogen levels for 7 to 11 days. After a single injection of Cyclofem and Mesigyna, both formulations showed equal contraceptive effect with inhibition of follicle maturation for some 30 days and ovulation, corpus luteum formation for some 60 days. Multicentre studies on the optimization of dosages of progestogens and estrogens in once-a-month injectables confirmed that the full doses of Cyclofem (DMPA 25 mg/estradiol cypionate 5 mg) and Mesigyna (NET-EN 50 mg/estradiol valerate 5 mg) are suitable for large scale clinical trials. Pharmacodynamics and progestogen/estrogen ratio study indicated the importance of not only the absolute amounts of the progestogen and estrogen but also of their ratio. Reduction of estrogen dose resulted in breakthrough ovulation with both Cyclofem and Mesigyna. Also, it is important to note that the second part of the injection cycle is dominated by the progestogen component of both monthly formulations. A longitudinal study indicated that there is no accumulation of norethisterone after 12 months of treatment with NET-EN 50 mg and estradiol valerate 5 mg. :About 1 million women in Latin America and China have used the 1st generation once-a-month combined injectable contraceptives Deladroxate and Chinese Injectable No. 1. Animal toxicity studies of Deladroxate found pituitary hyperplasia in rats, breast tumors in beagles, and accumulation of estradiol enanthate in the body. Thus, long-term toxicity and accumulation of Deladroxate need to be reevaluated. The erratic schedule of the Injectable No. 1 (initially administered on day 5 with 2 ampoules or 1 dose on day 5 and 1 dose on day 12; subsequent administration on the 10-12th day of the cycles) will confuse acceptors and family planning providers. Yet, a strict once-a-month cycle of Injectable No. 1 does not adequately protect against conception. Researchers have developed 2 improved once-a-month injectable formulations, Cyclofem and Mesigyna, to achieve good menstrual cycle control and high efficacy. The estrogen components of both formulations (estradiol valerate and cypionate) sufficiently elevate plasma estrogen levels for 7-11 days. One injection of both formulations inhibits follicle maturation for about 30 days and ovulation and corpus luteum formation for about 60 days. The doses of Cyclofem (25 mg depot-medroxyprogesterone acetate + 5 mg estradiol cypionate) and Mesigyna (50 mg norethindrone acetate + estradiol valerate) have been found to be optimal for use in large scale clinical trials. Not only are the absolute amounts of the progestogen and estrogen important, but also the progestogen/estrogen ratio. A lower estrogen dose in both Cyclofem and Mesigyna effects breakthrough ovulation. The progestogen component predominates the 2nd part of the injection cycle in both formulations. Norethindrone does not accumulate in the body after 12 months of treatment with Mesigyna.

journal_name

Contraception

journal_title

Contraception

authors

Sang GW

doi

10.1016/0010-7824(94)90033-7

subject

Has Abstract

pub_date

1994-04-01 00:00:00

pages

361-85

issue

eissn

0010-7824

issn

1879-0518

pii

0010-7824(94)90033-7

journal_volume

pub_type

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Pharmacodynamic effects of once-a-month combined injectable contraceptives.