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  1. 1
    Peer Reviewed

    Levonorgestrel and estradiol release from an improved contraceptive vaginal ring.

    Jackaniez TM

    Contraception. 1981 Oct; 24(4):323-39.

    A contraceptive vaginal ring containing levonorgestrel and estradiol was designed in which the drug is located in a 0.15 mm layer beneath a 0.25 mm overcoat at the ring's surface which controls the rate of steroid release. This design has been termed the "shell" ring. In vitro studies were carried out on the shell ring and also on 2 types of rings of earlier design, a homogenous ring and a shell ring without the rate-controlling overcoat. Levonorgestrel and estradiol were released in vitro at a constant rate of about 500 mcg/day and 300 mcg/day respectively, from shell rings of 9.2 mm cross-sectional diameter and 58 mm overall diameter. In the other 2 types of rings, a burst of steroid release was seen followed by a rapid fall in diffusion rates. Individual shell rings were used in clinical trials for 6 or 7 consecutive 21 day cycles with a 7 day nonuse interval between cycles. At the end of the study, they were returned to allow analysis and calculation of average steroid loss in vivo. In vivo, rings of 58 mm diameter were found to release levonorgestrel and estradiol at rates of 293 + or - 54 mcg/day and 183 + or - 34 mcg/day, respectively. Rings of 50 mm diameter had levonorgestrel and estradiol release rates of 252 + or - 34 mcg/day and 152 + or - 21 mcg/day, respectively. The release characteristics of the shell ring are such that it is expected to find a role in fertility control. All the studies reported in this issue of Contraception have used the same design of shell ring. (author's)
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