Oral contraceptives and the risk of gallbladder disease: a comparative safety study

Background: Recent concerns have been raised about the risk of gallbladder disease associated with the use of drospirenone, a fourth-generation progestin used in oral contraceptives. We conducted a study to determine the magnitude of this risk compared with other formulations of oral contraceptives. Methods: We conducted a retrospective cohort study using the IMS LifeLink Health Plan Claims Database. We included women who were using an oral contraceptive containing ethinyl estradiol combined with a progestin during 1997-2009. To be eligible, women had to have been taking the oral contraceptive continuously for at least six months. We computed adjusted rate ratios (RRs) for gallbladder disease using a Cox proportional hazards model. In the primary analysis, gallbladder disease was defined as cholecystectomy; in a secondary analysis, it was defined as hospital admission secondary to gallbladder disease. Results: We included 2 721 014 women in the cohort, 27 087 of whom underwent surgical or laparoscopic cholecystectomy during the follow-up period. Compared with levonorgestrel, an older second-generation progestin, a small, statistically significant in crease in the risk of gallbladder disease was associated with desogestrel (adjusted RR 1.05, 95% confidence interval [CI] 1.01-1.09), drospirenone (adjusted RR 1.20, 95% CI 1.16-1.26) and norethindrone (adjusted RR 1.10, 95% CI 1.06-1.14). No statistically significant increase in risk was associated with the other formulations of oral contraceptive (ethynodiol diacetate, norgestrel and norgestimate). Interpretation: In a large cohort of women using oral contraceptives, we found a small, statistically significant increase in the risk of gallbladder disease associated with desogestrel, drospirenone and norethindrone compared with levo norgestrel. However, the small effect sizes compounded with the possibility of residual biases in this observational study make it unlikely that these differences are clinically significant.