Quantitative model for the blood pressure-lowering interaction of valsartan and amlodipine.

AimsThe objective of this study was to develop a population pharmacokinetic (PK) and pharmacodynamic (PD) model to quantitatively describe the antihypertensive effect of combined therapy with amlodipine and valsartan. MethodsPK modelling was used with data collected from 48 healthy volunteers receiving a single dose of combined formulation of 10mg amlodipine and 160mg valsartan. Systolic (SBP) and diastolic blood pressure (DBP) were recorded during combined administration. SBP and DBP data for each drug alone were gathered from the literature. PKPD models of each drug and for combined administration were built with NONMEM 7.3. ResultsA two-compartment model with zero order absorption best described the PK data of both drugs. Amlodipine and valsartan monotherapy effects on SBP and DBP were best described by an I-max model with an effect compartment delay. Combined therapy was described using a proportional interaction term as follows: (D-1+D-2) +ALPHAx D-2). D-1 and D-2 are the predicted drug effects of amlodipine and valsartan monotherapy respectively. ALPHA is the interaction term for combined therapy. Quantitative estimates of ALPHA were -0.171 (95% CI: -0.218, -0.143) for SBP and -0.0312 (95% CI: -0.07739, -0.00283) for DBP. These infra-additive interaction terms for both SBP and DBP were consistent with literature results for combined administration of drugs in these classes. ConclusionPKPD models for SBP and DBP successfully described the time course of the antihypertensive effects of amlodipine and valsartan. An infra-additive interaction between amlodipine and valsartan when used in combined administration was confirmed and quantified.