Suggested guidelines for determining the trough-to-peak ratio of antihypertensive drugs.

The trough-to-peak (T:P) ratio is a measure of a drug's antihypertensive effects over a standard dosing interval. The T:P ratio was introduced by regulatory authorities without any details on how it was to be derived from clinical trial data. Differences in study design (sequential versus cross-over), techniques for recording blood pressure, methods of correcting for placebo responses, timing and duration of peak and trough effects, activity status of patients, use of responders only versus all subjects, and duration of antihypertensive therapy have made it difficult to interpret the clinical relevance of much of the existing data on the T:P ratio. Minimum standards for obtaining the T:P ratio over a 24 h dosing interval are proposed for use in future studies in order to obtain more precise and reproducible T:P ratios and to compare differences between compounds with greater reliability.