Integrating drug pharmacokinetics for phenotyping individual renin response to angiotensin II blockade in humans

Abstract

Renin release into plasma has been used to investigate the drug dose-dependence of renin-angiotensin system inhibition because it is proportional to the interruption of the permanent negative feedback loop of angiotensin II on renin secretion. We investigated the 24-hour between-subject differences in renin profiles by analyzing the time-dependence of individual renin responses in 16 mildly sodium-depleted normotensive subjects exposed in a 4-period crossover study to single oral doses of 8- and 16-mg (C8 and C16) candesartan cilexetil and 80- and 160-mg (V80 and V160) valsartan. C8 had a similar effect to V160 in terms of the increase in active renin concentration and decrease in blood pressure. C16 had the strongest effect and V80 the weakest effect on renin release. Within- and between-subject variability was more marked for valsartan pharmacokinetics than for candesartan pharmacokinetics and influenced variability in renin response. To eliminate some of the variability caused by the pharmacokinetics of each drug, we corrected the area under time curve of plasma renin levels by that of plasma drug levels to obtain an individual normalized index of renin release or "renin/pharmacokinetic index". In these experimental conditions, this index was found to be a reproducible individual characteristic affecting renin response, in addition to the pharmacokinetics and pharmacological properties of angiotensin II type-1 receptor antagonists. The pharmacokinetic-pharmacodynamic model of renin release described here could be of value for the identification and investigation of renin release abnormalities in patients with hypertension and for the comparison of renin-angiotensin system blockers.