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Infect Dis Obstet Gynecol. 2012;2012:137192. doi: 10.1155/2012/137192. Epub 2012 Feb 28.

Pharmacokinetic interactions between the hormonal emergency contraception, levonorgestrel (Plan B), and Efavirenz.

Author information

1
Division of Infectious Diseases, University of Colorado Denver, Aurora, CO, USA. monica.carten@ucdenver.edu

Abstract

OBJECTIVES:

Compare the Plan B levonorgestrel (LNG) area under the concentration- time curve (AUC(12)) prior to and with efavirenz (EFV). Design. Prospective, open-label, single-arm, equivalence study.

METHODS:

Healthy HIV-negative subjects underwent 12 hr intensive pharmacokinetic (PK) sampling following single dose LNG alone and after 14 days of EFV. Geometric means, Geometric Mean Ratios, and 90% confidence intervals (CI) are reported for PK Parameters. T-tests were utilized. Clinical parameters and liver function tests (LFTs) were assessed.

RESULTS:

24 women enrolled and 21 completed the study. With EFV, LNG AUC(12) was reduced 56% (95% CI: 49%, 62%) from 42.9 to 17.8 ng∗hr/mL, and maximum concentration (C(max)) was reduced 41% (95% CI: 33%, 50%) from 8.4 to 4.6 ng/mL. LNG was well tolerated with no grade 3 or 4 treatment-related toxicities.

CONCLUSIONS:

EFV significantly reduced LNG exposures. Higher LNG doses may be required with EFV. These results reinforce the importance of effective contraception in women taking EFV.

PMID:
22536010
PMCID:
PMC3299227
DOI:
10.1155/2012/137192
[Indexed for MEDLINE]
Free PMC Article
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