A multicenter study of levonorgestrel—Estradiol contraceptive vaginal rings I — Use effectiveness: An international comparative trial

Abstract

Contraceptive vaginal rings (CVRs) with approximate daily release rates of 250 to 290 μg of levonorgestrel and 150 to 180 μg of estradiol were manufactured in a shell design, with outside diameters of 50 mm or 58 mm. The rings were studied for contraceptive effectiveness and acceptability in multicentered trials involving 1,103 ring users. A comparison group of 533 women using the oral contraceptive, Nordette ∗ ∗ Nordette is a registered trademark of Wyeth-Pharma, Munster, WeSt Germany. , was studied simultaneously. Both first and all segment 1-year gross pregnancy rates among CVR users were less than 3 per 100, approximately the same as the pregnancy rates observed among users of Nordette. Continuation at 1 year was 50 per 100 users of the ring (all segments). This rate was significantly higher than or equal to the rate observed among the users of Nordette, depending upon the analytical treatment of subjects lost-to-follow-up. The profile of terminations was similar for the users of the 2 sizes of rings but differed from that of the Nordette acceptors. Gross l-year rates of termination for medical reasons ranged from 25 to 29 per 100 for the 3 regimens. Ring users were more likely to terminate for vaginal problems and pill users for headache, nausea and associated reasons. Problems relating to use of the regimen accounted for a significantly higher discontinuation rate among CVR than among Nordette users. These trials indicate that CVRs of this design are as effective in use and have continuation rates equal to and possibly superior to Nordette under the same study conditions.