Abstract: AIM: To study a reasonable algorithm of terminal half-life time (t_1/2z) in pharmacokinetics by the accuracy and precision.METHODS: The plasma concentration-time data of pu- erarin was simulated for 1000 subjects by using parameters of intravenous two-compartment models in the variations of 15%, 25% and 35%. Resampling 15, 25, 35, and 45 from the 1000 subjects were used to calculate t_1/2z by 4-point, 5-point, 6-point, all-point methods when there were different points in eliminate phase. The results of these methods were compared to the true value and expressed by accuracy and precision.RESULTS: The 5-point method can provide a t_1/2z with better accuracy and precision when there are four concentration points in eliminate phase, the 4-point method provide the one with better accuracy in three points in eliminate phase, 6-point method provide t_1/2z with better precision in both three and four points in eliminate phase. There is no reasonable t_1/2z in all four methods if there are two points in eliminate phase.CONCLUSION: Three concentration points should be at least included in eliminating phase for calculating a t_1/2z which is usually more reasonable in 4-points or 5-points method.

Key words: Terminal half-life time, Noncompartmental parameter, Pharmacokinetics