Pharmacokinetics and pharmacodynamics of oral tolvaptan in patients with varying degrees of renal function

The selective vasopressin V2-receptor antagonist tolvaptan is eliminated almost exclusively by non-renal mechanisms. As renal impairment can influence the pharmacokinetics of drugs even when eliminated by non-renal mechanisms, we evaluated the effect of renal insufficiency on the pharmacokinetics/pharmacodynamics of tolvaptan. Thirty-seven patients were grouped by a 24-h creatinine clearance (CrCL) and evaluated for 48h after a single 60mg oral dose in the fasting state. Mean tolvaptan exposure was 90% higher in the under 30-ml/min group compared with the over 60-ml/min group with individual values significantly but negatively correlated with increasing baseline CrCL. There was a greater and more rapid increase in urine output and free water clearance in the over 60-ml/min compared with the renal impaired groups, but they returned to baseline more quickly. Serum sodium increased more rapidly in the over 60 as opposed to the under 30-ml/min group, but overall maximum increases were similar across groups. Small decreases in mean CrCL and small increases in mean serum creatinine/potassium were independent of baseline CrCL. The percent fractional free water clearance with respect to CrCL was significantly but negatively correlated with increasing baseline CrCL. No unexpected adverse events were reported. Thus, renal impairment attenuated the increase in 24-h urine volume and free water clearance caused by tolvaptan, consistent with decreased nephron function in renal impairment. The delay in serum sodium increase was consistent with the longer duration needed to excrete sufficient water to cause the increase.