Abstract: AIM: To study the bioequivalence of endogenous drug of iodized lecithin. METHODS: The endogenous and other sources (diet) iodine need to be controled. By a two-period cross-over tria1, a total of 24 healthy volunteers were randomized to two groups to receive 9 iodized lecithin tablets (test or reference formulation). The concentrations of iodized lecithin in serum or urine were determined by arsenic-cerium catalytic spectrophotometric method. The pharmacokinetic parameters were measured by DAS2.1.1 software.RESULTS: The value added of the average net concentration of blood iodine are 16.8% (test formulation) and 19.0% (reference formulation), and the recovery rate of urinary iodine are 84.5% and 83.3%.The net excretion of urinary iodine were subtracted from the amount obtained on the drug dosing day, and the bioequivalence analysis was done according to the baseline-adjusted parameters (Ae_{0-24 h}: cumulative urinary excretion from 0 to 48 hours,R_max: maximal rate of urinary excretion). The test and reference preparations of iodized lecithin were bioequivalent.CONCLUSION: It is a complicated design for the study of the bioequivalence of endogenous drug. Various kinds of in vivo and in vitro factors have a great influence on the result, and background need to be deducted.

Key words: Endogenous drugs, Bioequivalence, Iodized lecithin, Pharmacokinetic