Bioavailability of levonorgestrel from intravaginal rings in women of low income groups.
Two types of intravaginal rings (IVR) containing 50-128 mg of levonorgestrel (LNOG) and 28-60 mg of estradiol were inserted in 18 apparently normal subjects belonging to the low socioeconomic group on day 5 of the cycle. A total of 120 cycles were studied with cyclic insertion and withdrawal. Data on menstrual cycle changes were noted. For bioavailability study, blood samples were collected twice weekly for a period of one month in the first cycle in 8 women. All the plasma samples were analysed for LNOG and progestrone by RIA. Cycle control was excellent in IVR users. Expulsion of the ring was noted in 4 instances. The plasma LNOG levels were found to reach a peak level ranging from 2.7-7.5 ng/ml within 4 days after the IVR insertion. In between day 9 to 24, the plasma levels appeared to be almost steady, and once the ring was removed, the levels dropped off rapidly. The mean plasma LNOG calculated during the steady-state period of the cycle ranged from 1.6-5.1 ng/ml. These mean LNOG levels were found to be inversely correlated with skin-fold at triceps. In all the subjects ovulation was found to be inhibited, as reflected by plasma progesterone values. The range of release rates calculated from plasma steady-state values was 51-119 micrograms/day. The average release rates over the entire period of observation based on area under curve were 102-200 micrograms/day. On the other hand, the release rates obtained from the residual drug in the ring after a period of use ranged from 184-259 micrograms/day.
D000293:Adolescent; D000328:Adult; D001682:Biological Availability; D005260:Female; D006207:Half-Life; D006801:Humans; D007700:Kinetics; D016912:Levonorgestrel; D008597:Menstrual Cycle; D009644:Norgestrel / Q000008:administration & dosage / Q000378:metabolism*; D009748:Nutrition Disorders / Q000378:metabolism; D011374:Progesterone / Q000097:blood; D012959:Socioeconomic Factors; D014621:Vagina
D009644:Norgestrel; D011374:Progesterone; D016912:Levonorgestrel