RHL Commentary by Mario Festin
EVIDENCE SUMMARY
Combined oral contraceptives (COCs) have an estrogen and a progestogen component. Existing progestogen compounds can be classified as first-, second- and third-generation.
First-generation progestogens include, among others, norethisterone (NET), norethindrone (NE), ethynodiol diacetate, and lynestrenol (LYN). Levonorgestrel (LNG) and norgestrel (NG) are the second-generation progestogens, and third-generation progestogens include desogestrel (DSG), gestodene (GSD) and norgestimate (NGM). Second-generation progestogens were introduced into the market in the 1970s and third-generation progestogens were introduced a decade later. Currently, LNG is probably the most widely used progestogen and is predominantly combined with 30 µg ethinyl estradiol in combined oral contraceptive pills.
The review compares currently available low-dose COCs (containing different progestogens) in terms of their effectiveness, safety and acceptability (protection against pregnancy, cycle control, side-effects and use continuation rates). Twenty-two trials (including 18 sponsored by the pharmaceutical industry) are included. Among these, in only five trials there was an attempt at blinding.
Method discontinuation was lower with second- compared with first-generation progestogens (relative risk [RR]: 0.79; 95% confidence interval [CI]: 0.69–0.91). Cycle control appeared to be better with second- compared with first-generation progestogens for both mono- (RR: 0.69; 95% CI: 0.52-0.91) and triphasic (RR: 0.61; 95% CI: 0.43–0.85) preparations. GSD (3rd gen.) and LNG (2nd gen.) yielded similar rates for contraceptive effectiveness, spotting, breakthrough bleeding and the absence of withdrawal bleeding. However, there was less intermenstrual bleeding in the GSD group (RR: 0.71, 95% CI: 0.55–0.91). All acceptability indices showed that third- and second-generation (LNG) progestogens were preferred over those containing first-generation progestogens. More pregnancies occurred when pills containing 20 µg ethinyl estradiol (EE) were used. Compared with pills containing DSG, those with GSD yielded better cycle control, although the continuation rate was higher in women using DSG-containing pills. The results of trials of pills containing drospirenone (DRSP) were similar to those with DSG with regard to pregnancy prevention, cycle control and side-effects.
The full RHL commentary also includes sections on: Relevance
- Magnitude of the problem
- Applicability of the results
- Implementation of the intervention
Research
References
This document should be cited as: Mario Festin. Progestogens in combined oral contraceptives for contraception: RHL commentary (last revised: 8 March 2006). The WHO Reproductive Health Library, No 9, Update Software Ltd, Oxford, 2006. www.rhlibrary.com
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