Comparative study on the efficacy acceptability and side effects of a contraceptive pill administered by the oral and the vaginal route: an international multicenter clinical trial.

TLDR: The vaginal route of administration appears to be as acceptable and efficacious as the oral route, and involuntary pregnancy rates after 1 year were not statistically significantly different between the two groups.

Abstract: The objective of this multicenter randomized clinical trail was to compare the efficacy acceptability and occurrence of side effects associated with the oral versus vaginal route of administration of contraceptive pills. This study started in June 1987 and data collection extended up to April 1992 at family planning clinics and research centers members of the South to South Cooperation in Reproductive Health in seven countries of the developing world. The 819 subjects were from 17 to 39 years of age had already had at least one pregnancy had had regular menstrual cycles for 3 months before were exposed to the risk of pregnancy and were not using any other method of contraception. 424 were randomly assigned to use the pills orally (which contained 250 mcg levonorgestrel and 50 mcg ethinyl estradiol) whereas 395 inserted the pills vaginally. 625 subjects completed at least 6 months of use 326 used the pills orally and 299 used the pills vaginally. 385 subjects completed 1 year of pills use 201 in the oral group and 184 in the vaginal group. The 1-year discontinuation rate per 100 subjects per year for the oral group was 34.71 +or- 2.42 while it was 36.35 +or- 2.53 for the vaginal group. This difference was not statistically significant. The only single reason of statistically significant difference for discontinuation was "desire for pregnancy" (p = 0.444). Paired value analysis of subjects completing 12 months of study showed that women in the oral group had a statistically significant increase in weight from a mean of 55.8 kg at admission to a mean of 56.9 kg at 6 months (p < 0.05) and 57.3 kg at 1 year (p = 0.05). The mean weight of the vaginal group increased from 56.52 kg to 57.22 kg (p = 0.036) at 12 months. Significantly more complaints of vaginal discharge were recorded in women using the pills by the vaginal route (p = 0.001). However only one subject discontinued the pills because of vaginal discharge.