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Title: Levonorgestrel concentrations during use of levonorgestrel rod (LNG ROD) implants
Authors: Sivin, I.
Lähteenmäki, P.
Ranta, S.
Darney, P.
Klaisle, C.
Wan, L.
Mishell Jr., D.R.
Lacarra, M.
Viegas, O.A.C. 
Bilhareus, P.
Koetsawang, S.
Piya-Anant, M.
Diaz, S.
Pavez, M.
Alvarez, F.
Brache, V.
LaGuardia, K.
Nash, H.
Stern, J.
Keywords: contraception
levonorgestrel concentrations
rod implants
Issue Date: Feb-1997
Citation: Sivin, I., Lähteenmäki, P., Ranta, S., Darney, P., Klaisle, C., Wan, L., Mishell Jr., D.R., Lacarra, M., Viegas, O.A.C., Bilhareus, P., Koetsawang, S., Piya-Anant, M., Diaz, S., Pavez, M., Alvarez, F., Brache, V., LaGuardia, K., Nash, H., Stern, J. (1997-02). Levonorgestrel concentrations during use of levonorgestrel rod (LNG ROD) implants. Contraception 55 (2) : 81-85. ScholarBank@NUS Repository.
Abstract: In a three-year randomized trial that included 398 women, blood samples were collected for the purpose of assaying levonorgestrel concentrations in women using a new two-rod contraceptive implant system or an earlier implant formulation, Norplant®-2 implants. Sample collection was at 1, 3, 6, 9, and 12 months after placement and semiannually thereafter through three years. Resulting assays and analyses showed that levonorgestrel concentrations of each implant formulation decreased significantly with time after placement, with increasing body weight, and with ponderal index. In the third year, several measures indicated that concentrations of the contraceptive drug were higher in women using the LNG ROD implants than in users of the original formulation. No pregnancies occurred among women in either group in the three years. This study provides evidence that the minimum levonorgestrel concentration needed to protect against pregnancy is below 200 pg/ml, and possibly is below 175 pg/ml.
Source Title: Contraception
ISSN: 00107824
DOI: 10.1016/S0010-7824(96)00276-4
Appears in Collections:Staff Publications

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