Trough: peak ratio and twenty-four-hour blood pressure control.

UNLABELLED

DEFINITION OF TROUGH: PEAK RATIO: Applied to an antihypertensive drug, the term trough: peak ratio provides an index of how well the antihypertensive effect is sustained over the dose interval. This ratio is usually expressed as a percentage and is determined from the ratio of the blood pressure reduction at trough, i.e. at the end of the dose interval and before the next dose is administered, relative to the blood pressure reduction at the time of the peak drug effect. According to guidelines issued by the United States Food and Drug Administration, 50% is the minimum requirement for an acceptable trough: peak ratio.

TIMING OF MEASUREMENT

Unfortunately, the Food and Drug Administration has not produced guidelines describing the methodology, required to define the trough: peak ratio, apart from the requirement that account be taken of placebo effects. However, although the timing of the trough measurement is defined, the response to an antihypertensive drug is influenced by intra- and interindividual variability, and to measure the peak response it is necessary to take multiple blood pressure measurements throughout the dose interval. This will take account not only of diurnal variations in an individual subject's blood pressure but also of interindividual variability in the timing and magnitude of the peak response to treatment.

CONCLUSIONS

Assuming it is appropriately measured, the trough: peak ratio is a useful index of the consistency of the antihypertensive response throughout the dose interval and of the optimal dose frequency.