Objective: To search for the best method of calculating trough:peak ratio. Methods:Thirty three patients with mild
to moderate essential
hypertension were studied.After 2 week's treatment with placebo,they were randomizedly treated with amlodipine (AM, n =16)or nifedipine gastrointestinal therapeutic system(GITS)(NI, n =17)for a further 4 weeks.The efficacy of drugs were evaluated by office blood pressure and ambulatory blood pressure monitoring.Trough value,peak value and trough:peak ratio were
calculated by different methods. Results:The blood pressure decreased significantly in both groups.There were significant differences between peak values calculated by different methods.The peak value and time to peak of individual subjects varied greatly.The trough values were similar when computed by different methods.In AM group,the systolic blood pressure and diastolic blood pressure trough:peak ratios calculated by global method were 63% and 55% respectively,that calculated by individual method were (30±42)% and (25±48)% respectively.In NI group,they were 85%,81% and (55±34)%,(52±42)% respectively. Conclusion:The peak value and time to peak of individual subjects varied significantly.The peak values calculated over 2h in the whole 24 hours interval of dosing by individual approach is better.The global approach might lead to overestimation of trough:peak ratio.