The influence of dietary sodium content on the pharmacokinetics and pharmacodynamics of fimasartan

Namyi Gu,1,2 Joo-Youn Cho,3 Kwang-Hee Shin,4 In-Jin Jang,3 Moo-Yong Rhee2,5 1Department of Clinical Pharmacology and Therapeutics, 2Clinical Trial Center, Dongguk University College of Medicine and Ilsan Hospital, Goyang, 3Department of Clinical Pharmacology and Therapeutics, Seoul National University College of Medicine and Hospital, Seoul, 4Pharmacotherapy & Translational Research Lab., College of Pharmacy, Research Institute of Pharmaceutical Sciences, Kyungpook National University, Daegu, 5Cardiovascular Center, Dongguk University College of Medicine and Ilsan Hospital, Goyang, Republic of Korea Abstract: A low sodium diet enhances the hemodynamic effect of renin–angiotensin system blockers. It was suggested that the substrates of P-glycoprotein or cytochrome P450 3A4 were reduced on a high sodium diet. This study aimed to investigate the influence of high sodium diet on the pharmacokinetics and pharmacodynamics of fimasartan, which is a substrate of cytochrome P450 3A4 but not P-glycoprotein. The study design was a two-diet, two-period, two-sequence, randomized, open-label, and crossover with 1-week washout for diet. Eligible subjects were fed with either low sodium (50 mEq/day) diet or high sodium diet (300 mEq/day) for 7 days in the first hospitalization period and the other diet in the second period. On the seventh morning of each period, subjects received a single dose of fimasartan 60 mg in a fasted state. The serial plasma concentrations of fimasartan, serum aldosterone concentration (SAC), and plasma renin activity (PRA) were measured for pharmacokinetic–pharmacodynamic analysis. Sixteen subjects completed the study satisfying the compliance test for diets. Although the mean systemic exposure of fimasartan is slightly (≈10%) decreased on a high sodium diet, the difference was not statistically or clinically significant (P>0.05). The SAC and PRA after fimasartan administration were highly dependent on their baseline levels. The dietary sodium content influenced the baseline of SAC and PRA, but did not influence the ratio change of SAC and PRA after fimasartan treatment. The ratio change of SAC after fimasartan treatment was correlated to the systemic exposure of fimasartan (P0.05). In conclusion, the pharmacokinetics of fimasartan and ratio changes of SAC and PRA after fimasartan treatment were not significantly influenced by dietary sodium content. Keywords: aldosterone, renin activity, angiotensin receptor blocker, aldosterone, renin, cytochrome P450 3A4, P-glycoprotein, healthy, sodium diet