Objective: The progestogen-only method of emergency contraception, levonorgestrel, is one of the effectiveness in preventing expected pregnancies. The comparative bioavailability was carried out on levonorgestrel tablets (0.75 mg) from two different sources (Hungarian and Thai made).
Method: Eighteen healthly female volunteers were given a single oral dose of 0.75 mg tablets in a crossover design. Serum
levonorgestrel concentration was determined by radio-immunoassay. The pharmacokinetic analysis of serum levonorgestrel concentration from each treatment was established. The comparative bioavailability of the two products was determined by the analysis of variance (ANOVA) for two way crossover design.
Results: The results found that the mean peak (X+SD)serum concentration (Cmax) of the Thai –made pill and Hungarianpill
were 1.18 + 0.12 and 1.14 + 0.10 ng/ml, respectively. The 90% confidence interval for the difference of log Cmax mean
was 99.54 – 120.78%. The time to peak serum concentration (Tmax) of the Thai-made pill and Hungarian-pill were 1.56 +
0.73 and 1.58 + 0.67 hrs, respectively. The different time of peak serum levonorgestrel concentration was 1.27%. The mean
area under the curve (AUC) of Thai-made pill and Hungarian-pill were 2.14 + 0.21 and 2.09 + 0.16 ng.h/ml, respectively.
The 90% confidence interval for the difference of log AUC mean was 103.27 – 121.89%.
Conclusion: The persent study revealed that the 90% confidence interval for the difference of log Cmax mean and log AUC mean were in the criteria of acceptance, which should be within 80-125%. So, the authors can conclude that the Thai- made pill was bioequivalent to the Hungarian-pill.

Keywords: Bioequivalence, Postcoital contraception, Emergency contraception, Levonorgestrel