Clinical evidence is still insufficient to confirm the birth control pill is an effective strategy to improve painful menstruation in women with endometriosis, according to a recent review.
The study “Modern combined oral contraceptives for treatment of pain associated with endometriosis” was published in the Cochrane Library.
Birth control pills, also called combined oral contraceptives, are widely used as a therapy for pain in women living with endometriosis, but evidence supporting that strategy’s effectiveness remains limited.
A group of researchers looked for published clinical studies — specifically randomized controlled trials — that assessed birth control pills as pain-relieving therapy in endometriosis. They searched several databases, including the trial registers ClinicalTrials.gov and the World Health Organization Clinical Trials Registry Platform (WHO ICTRP).
The search retrieved five trials, but only three of them, comprising a total of 404 women, included data suitable for further analysis.
In two small trials, treatment with the birth control pill was linked to improvements in self-reported pain at the end of treatment when compared with women who received a placebo (control participants). Researchers assessed the pain outcomes via the dysmenorrhoea (painful menstruation) verbal rating scale and a dysmenorrhoea visual analogue scale.
The quality of the evidence, however, was poor and the trials may have lacked independence due to substantial involvement of the pharmaceutical company funding the trials, researchers noted.
A third, small-scale trial with 50 women compared the effectiveness of birth control pills to goserelin acetate (sold by AstraZeneca as Zoladex, e.g.), an implant used as management therapy for endometriosis, including as a pain reliever and to reduce endometrial lesions.
However, at the end of the treatment, women treated with goserelin had no menstruation (amenorrhea), so no comparison between groups was made.
At six-month follow-up, researchers found no clear evidence supporting a difference between both treatments — birth control pills versus goserelin — in improving dysmenorrhoea. Once again, researchers found high risk of bias in this study.
Overall, “based on the limited evidence from two trials at high risk of bias and limited data for the prespecified outcomes for this review, there is insufficient evidence to make a judgment on the effectiveness of the COCP [combined oral contraceptive pill] compared with placebo and the findings cannot be generalized,” they wrote.
“Further research is needed to fully evaluate the role of COCPs [combined oral contraceptive pills] in managing pain-related symptoms associated with endometriosis,” the study concluded.