Progestin-only contraceptive rings.
Several progestin-only long acting contraceptives are currently available in the form of implants or injectables. Vaginal rings are another contraceptive option in the final stages of development. These steroid-containing polymer rings are placed in the vagina, providing relatively constant drug release, thus allowing for lower effective doses. Vaginal rings have the advantage of being user-controlled and non-provider dependent, and their use is non-coital related. The first clinical study with medroxyprogesterone acetate vaginal rings was published in 1970. Since then numerous clinical trials testing different steroids and doses have followed. A large Phase III multicenter clinical trial with a levonorgestrel ring, releasing 20 microg/day, was coordinated and sponsored by WHO. The cumulative one-year pregnancy rate was 4. 5%. The principal reasons for discontinuation were menstrual disturbances (17.2%), followed by frequent expulsion of the ring (7. 1%), and vaginal symptoms (6.0%). The finding of erythematous lesions in the vagina in some women has led to the development of a more flexible device. Collaboration with industry should facilitate the manufacture of a redesigned levonorgestrel ring with a higher release rate. The Population Council is also developing a vaginal ring containing Nestorone for 6 months of continuous use. Ovulation inhibition was achieved in over 97% of the segments studied, with rings releasing either 50, 75, or 100 microg/day. No pregnancies occurred in women using the low-dose ring, while one pregnancy each occurred in the intermediate- and high-dose ring groups for a 6-month cumulative pregnancy rate of 0.0, 1.9, and 2.1%. Bleeding irregularities were common. Nestorone is orally inactive; therefore this ring is also excellent for use in lactating women.
Brache
V
V
PROFAMILIA Inc., Biomedical Research Department, P.O. Box 1053, Santo Domingo, Dominican Republic. biomedica@codetel.net.do
Alvarez-Sanchez
F
F
Faundes
A
A
Jackanicz
T
T
Mishell
D R
DR
Lähteenmäki
P
P
D000282:Administration, Intravaginal; D003271:Contraceptive Agents, Female / Q000008:administration & dosage* / Q000097:blood / Q000592:standards; D003692:Delayed-Action Preparations / Q000493:pharmacokinetics / Q000592:standards; D004343:Drug Implants / Q000493:pharmacokinetics / Q000592:standards; D005260:Female; D006801:Humans; D011247:Pregnancy; D011372:Progestins / Q000008:administration & dosage* / Q000097:blood / Q000592:standards
D003271:Contraceptive Agents, Female; D003692:Delayed-Action Preparations; D004343:Drug Implants; D011372:Progestins