Levonorgestrel concentrations during use of levonorgestrel rod (LNG ROD) implants

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, an...

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Bibliographic Details
Published in:Contraception (Stoneham) 1997-02, Vol.55 (2), p.81-85
Main Authors: Sivin, Irving, Lähteenmäki, Pekka, Ranta, Sirpa, Darney, Philip, Klaisle, Cindy, Wan, Livia, Mishell, Daniel R., Lacarra, Maria, Viegas, Osborn A.C., Bilhareus, Prapas, Koetsawang, Suporn, Piya-Anant, Manee, Diaz, Soledad, Pavez, Margarita, Alvarez, Francisco, Brache, Vivian, LaGuardia, Katherine, Nash, Harold, Stern, Janet
Format: Article
Language:English
Subjects:
Adolescent
Adult
Age Factors
Analysis of Variance
Biological and medical sciences
Birth control
Body Weight
contraception
Contraceptive Agents, Female - administration & dosage
Contraceptive Agents, Female - blood
Contraceptive Agents, Female - standards
Drug Implants
Female
Gynecology. Andrology. Obstetrics
Hormonal contraception
Humans
implants
Levonorgestrel - administration & dosage
Levonorgestrel - blood
Levonorgestrel - standards
levonorgestrel concentrations
Medical sciences
Population
Pregnancy
Pregnancy Rate
rod implants
Time Factors
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Description
Summary: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.
ISSN:0010-7824
1879-0518
DOI:10.1016/S0010-7824(96)00276-4