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The pharmacokinetics of 750 μg levonorgestrel following administration of one single dose or two doses at 12- or 24-h interval

Publication Date
DOI: 10.1016/s0010-7824(01)00276-1
  • Original Research Article
  • Pharmacology


Abstract The administration of two tablets of 750 μg levonorgestrel at a 12- to 24-h interval has been shown to be a safe and effective means of emergency contraception, and Norlevo/Vikela (N/V) is a dedicated product for this indication. The aim of this study was to characterize the plasma pharmacokinetics of levonorgestrel following a single N/V tablet administration and following a second administration, 12 or 24 h after the first one in young, healthy, female volunteers under the same conditions as during clinical use. This was an open, observer-blind, randomized study with three parallel groups and three treatments performed in 24 white female volunteers randomized into three groups of eight participants, each receiving one of the following treatments: Group A, one tablet of 750 μg levonorgestrel at time −12 h and one tablet at time 0; Group B, one tablet of 750 μg levonorgestrel at time 0; Group C, one tablet of 750 μg levonorgestrel at time −24 h and one tablet at time 0. All treatments started between Day 2 and Day 6 of the menstrual cycle. Plasma levonorgestrel levels were measured at regular intervals from time 0 up to 36 h with a validated radioimmunoassay. The results of this study show that after either one single or two administrations of a tablet containing 750 μg levonorgestrel, levonorgestrel is rapidly absorbed. The absorption, distribution, and elimination profiles of levonorgestrel following the three different treatments were similar. It also indicates that 12 or 24 h after administration there remains a significant level of plasma levonorgestrel. In conclusion, this study reinforces clinical guidelines recommending that N/V tablets for emergency contraception be administered 12 to 24 h apart because levonorgestrel is present in plasma between the two administrations.

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