FIRST WEEK DRUG CONCENTRATIONS IN WOMEN WITH LEVONORGESTREL ROD OR NORPLANT(R) CAPSULE IMPLANTS

Forty-two healthy women volunteered to have blood samples drawn at 2, 4, 8, 24, 48, and 168 h (7 days) following placement of levonorgestrel -releasing rod (LNG rod) or of Norplant(R) capsule implants to permit measurement of drug concentrations. Three clinics recruited 10 women e ach, half of whom used each type of implant. Twelve additional subject s were later enrolled at one site to provide greater detail for the ca psule implants. Throughout the week, women with Norplant implants had apparently higher mean drug concentrations than did women with LNG rod implants, but the differences were significant only in the first 48 h after placement (p < 0.05). Maximum levels for capsule implants were found at the 24-h sample (mean, 1358 to 1474 pg/mL) and for the LNG ro d implants at 48 h (772 pg/ml). Body weight was negatively correlated with levonorgestrel concentrations at all times (p < 0.05). For severa l sampling times, differences between clinics in mean concentrations w ere statistically significant after weight adjustment. Despite differe nces by implant type, weight, or clinic location, drug concentrations compatible with contraceptive effect were attained within 24 h in user s of LNG rod or of Norplant implants, insofar as all women had levonor gestrel concentrations above 250 pg/mL at the 24-h sample. (C) 1997 El sevier Science Inc. All rights reserved.