ABSTRACT
Contraceptive methods for breastfeeding women should be safe for the mother and infant and should not interfere with lactation. Progestin-only methods meet these conditions and can be used from the sixth week postpartum. Because all progestins are excreted in milk, those that are insufficiently active by the oral route are preferable to avoid any possible effect on the baby. These steroids, however, must be administered to the mother by a non-oral route. Initially, progesterone was administered subdermally to test this concept. Subsequently, a progesterone vaginal ring was developed to be used continuously for 3 to 4 months and replaced with a new device, as needed, until weaning. Clinical trials have shown a high contraceptive efficacy (over 98.5%) and safety. The gross continuation rate of this method is approximately 40% at 12 months of use, with use-related problems being the main reason for discontinuation (26.8%). Currently, a Nestorone vaginal ring is under development, delivering 50 microg of Nestorone per day. It may be used continuously for up to one year, even if weaning occurs earlier. Both of these progestin-only rings prolong lactational amenorrhea to 10 to 12 months, which represents a health benefit and convenience for many women. The registration of the progesterone vaginal ring, developed as a contraceptive method to be used exclusively during lactation, has been approved in Chile and Perú. The fact that it is a user-controlled long-term contraceptive that delivers a natural hormone makes it an attractive option for many women.
Subject(s)
Lactation/drug effects , Norprogesterones/administration & dosage , Administration, Intravaginal , Adult , Amenorrhea/etiology , Breast Feeding , Contraceptive Agents, Female/administration & dosage , Contraceptive Agents, Female/adverse effects , Contraceptive Agents, Female/standards , Delayed-Action Preparations , Drug Evaluation , Drug Implants/adverse effects , Drug Implants/standards , Female , Follow-Up Studies , Humans , Infant , Infant, Newborn , Male , Menstrual Cycle/drug effects , Norprogesterones/adverse effects , Norprogesterones/standards , Pilot Projects , Pregnancy , Pregnancy RateABSTRACT
The clinical performance and the in vivo release rate of a single 4-cm Nestorone subdermal implant were investigated. Implants manufactured by two different procedures were compared. Volunteers were 70 healthy women of proven fertility. Forty women provided blood samples twice a week in the pretreatment cycle and for 5-6 weeks at 6-month intervals during treatment. Additional control cycles (n = 31) were studied in 19 Copper T users. No pregnancy occurred in 1570 woman-months. Nestorone plasma levels (x +/- S.E.) declined from 112 +/- 8 to 86 +/- 3 pmol/L (Implant A) and from 145 +/- 8 to 57 +/- 5 pmol/L (Implant B) from the first to the 24th month. Progesterone levels were < 9.5 nmol/L in 166 (93%) of 178 blood samplings taken during treatment. Progesterone levels > 16 nmol/L were found in only 7 sampling periods (3.9%) in treated women and in 70 (98.6%) out of 71 control cycles. No ovulation occurred with Nestorone plasma levels above 105 pmol/L. No abnormal changes were observed in plasma lipoproteins or other clinical chemistry parameters during treatment. The implants were well tolerated. The most frequent complaint was the occurrence of irregular bleeding. Enlarged follicles found during pelvic examination in 8 subjects (11.4%) disappeared spontaneously in 10 days to 6 weeks. Implants were removed because of medical (n = 10, 14.3%) or personal reasons (n = 6, 8.6%) or at the 24th month of treatment (n = 54, 77.1%). The estimated average daily in vivo release rate of Nestorone was 45-50 micrograms/day. A single Nestorone subdermal implant affords efficient contraceptive protection during two years.
