Combined oral contraceptive pill (OCP) as treatment for primary dysmenorrhoea

Dysmenorrhoea refers to the occurrence of painful menstrual cramps and is a common gynaecological complaint. Research as early as 1937 has shown that dysmenorrhoea responds favourably to ovulation inhibition, and that the synthetic hormones in the combined oral contraceptive pill can be used to treat dysmenorrhoea. These hormones act by suppressing ovulation and lessening the endometrial lining of the uterus. Therefore, menstrual fluid volume decreases along with the amount of prostaglandins produced, in turn effectively reducing dysmenorrhoea by decreasing uterine motility, and thus uterine cramping. The use of combined oral contraceptive pills (OCP) has been advocated as a treatment for primary dysmenorrhoea since their introduction for general use in 1960. There is evidence from epidemiological studies of general populations that combined OCPs can effectively treat dysmenorrhoea.

The objective of this review is to determine the efficacy of combined oral contraceptive pills for the treatment of primary dysmenorrhoea.

Electronic searches for relevant randomised controlled trials (RCTs) of the Cochrane Menstrual Disorders and Subfertility Group Register of controlled trials, CCTR, MEDLINE, EMBASE, and CINAHL, were performed. Attempts were also made to identify trials from the National Research Register, the Clinical Trials Register and the citation lists of review articles and included trials.

The inclusion criteria were RCTs that compared all types of combined oral contraceptives (oestrogen/progestogen) with other combined oral contraceptives, placebo, no treatment, or treatment with nonsteriodal anti-inflammatory drugs (NSAIDs) in the treatment of primary dysmenorrhoea. The main outcome measures were pain relief, adverse effects, additional analgesics required and time off work or school.

Nine trials were identified that appeared to fulfil the initial criteria for this review. Of these nine trials, four were excluded, two at further investigation revealed a lack of randomisation and two included combined oral contraceptives that are now discontinued due to very high oestrogen content. Of the remaining five RCTs, four were included in the meta-analysis (Buttram 1969; Cullberg 1972; GPRG 1968; Nakano 1971). The results of the other trial (Matthews 1968) were included in the text of the review for discussion because data were not available in a form that allowed it to be combined in a meta-analysis. Data for all outcomes were in dichotomous form and the Peto odds ratio was used in the meta-analysis for all comparisons.

Combined OCPs with medium dose oestrogen (>35 mcg) and 1st/2nd generation progestogens were shown to be more effective than placebo for pain relief. However, there was significant heterogeneity in the results from different studies and when data were analysed with a random effects model, the confidence intervals increased and the results became statistically non-significant. For the other outcomes, there was a significant difference in favour of OCPs when compared to placebo for the outcome of absence from work or school, and there was no difference between the treatment groups and placebo in the number of adverse effects experienced.

No conclusions can be made about the efficacy of commonly used modern lower dose combined oral contraceptives for dysmenorrhoea. While there is some evidence from four RCTs that combined OCPs with medium dose oestrogen and 1st/2nd generation progestogens are more effective than placebo it should be emphasised that the studies were small, of poor quality and all included much higher doses of hormones that those commonly prescribed today. Therefore no recommendations can be made regarding the efficacy of modern combined oral contraceptives.