Abstract
AIMS: Quinine is often used to prevent muscle cramps in patients with chronic renal failure. A standard dose of 300 mg at bedtime is usually recommended, but little is known about the pharmacokinetics of quinine in the presence of renal failure. METHODS: We studied the pharmacokinetics of quinine in eight normal subjects and eight patients with chronic renal failure on haemodialysis after a single oral dose of quinine sulphate (300 mg). RESULTS: The concentration of alpha1-acid glycoprotein (AAG), the major binding protein for quinine, was increased in haemodialysis patients compared with control subjects (1.52 g l-1 vs 0.63 g l-1 [mean difference 1.033; 95% CI 0.735, 1.330]) whereas albumin levels were decreased (30 g l-1 vs 40 g l-1 [mean difference 9.5; 95% CI 3.048, 15.952]). Accordingly, the free fraction of quinine was decreased (0.024 vs 0.063 [mean difference 0.0380; 95% CI 0.0221, 0.0539]) and the apparent volume of distribution tended to decrease (0.95 l kg-1 vs 1.43 l kg-1 [mean difference 0.480; 95% CI 0.193, 1.154]). The quinine binding ratio correlated with the plasma concentration of AAG but not that of albumin. The clearance of free (unbound) quinine was increased in haemodialysis patients compared with controls (67.9 ml min-1 kg-1 vs 41.1 ml min-1 kg-1 [mean difference -26.8; 95% CI, -56.994, 3.469]), and the area under the curve (AUC) of the two main metabolites, 3-hydroxyquinine and 10,11-dihydroxydihydroquinine were increased. CONCLUSIONS: In patients with chronic renal failure, there is an increase in plasma protein binding and in the clearance of free drug, resulting in lower plasma concentration of free quinine.