Pharmacokinetic-pharmacodynamic model for perindoprilat regional haemodynamic effects in healthy volunteers and in congestive heart failure patients

Aims We compared the relationships between the plasma concentrations (C) of perindoprilat, active metabolite of the angiotensin I-converting enzyme in hibitor (ACEI) perindopril, and the effects (E) induced on plasma convertin g enzyme activity (PCEA) and brachial vascular resistance (BVR) in healthy volunteers (HV) and in congestive heart failure (CHF) patients after single oral doses of perindopril. Methods Six HV received three doses of perindopril (4, 8, 16 mg) in a place bo-controlled, randomized, double-blind, crossover study whereas 10 CHF pat ients received one dose (4 mg) in an open study. Each variable was determin ed before and 6-12 times after drug intake. E (% variations from baseline) were individually related to C (ng ml(-1)) by the Hill model E=E-max.C-gamm a/( CE50gamma + C-gamma). When data showed a hysteresis loop, an effect com partment was used. Results (means +/-s.d.) In HV, relationships between C and E were direct wh ereas in CHF patients, they showed hysteresis loops with optimal k(e0) valu es of 0.13 +/- 0.16 and 0.13 +/- 0.07 h(-1) for PCEA and BVR, respectively. For PCEA, with E-max set to -100%, CE50 = 1.87 +/- 0.60 and 1.36 +/- 1.33 ng ml(-1) (P = 0.34) and gamma = 0.90 +/- 0.13 and 1.11 +/- 0.47 (P = 0.23) in HV and CHF patients, respectively. For BVR, E-max=-41 +/- 14% and -60 /- 7% (P = 0.02), CE50 = 4.95 +/- 2.62 and 1.38 +/- 0.85 ng ml(-1) (P = 0.0 2), and gamma = 2.25 +/- 1.54 and 3.06 +/- 1.37 (P = 0.32) in HV and CHF pa tients, respectively. Conclusions Whereas concentration-effect relationships were similar in HV a nd CHF patients for PCEA blockade, they strongly differed for regional haem odynamics. This result probably expresses the different involvements, in HV and CHF patients, of angiotensinergic and nonangiotensinergic mechanisms i n the haemodynamic effects of ACEIs.