Factors contributing to variability in drug pharmacokinetics. IV. Renal excretion.

The renal excretion of drugs is mainly controlled by three factors: glomerular filtration, tubular secretion and tubular reabsorption. Only relatively polar drugs are excreted in appreciable amounts by the kidneys. Factors affecting renal excretion of drugs include: kidney function, protein binding, urine pH and urine flow. Impaired renal function may lead to a clinically significant accumulation of drugs eliminated by the kidneys, if more than 50% of the dose is normally excreted unchanged in the urine and the renal function is less than 50% of the normal value. Successful removal of a drug by dialysis requires that it possesses a polar character, low protein binding and a small to moderate volume of distribution.