Is the removal of parent drug and drug metabolites from the body. The kidneys account for the majority of drug excretion. Healthy kidneys serve to limit the duration and intensity of drug effects. Decreased kidney function prolongs the duration of action and intensity of drug effects. The basic structural and functional unit of the kidney. Controls blood volume, blood pressure, blood ph and solute (including drug) excretion. Drugs enter the kidney from the renal artery. Hydrostatic pressure within the glomerular capillaries force low molecular weight drugs into the renal tubules. 120 ml/min/1. 73m2 or about 20% of total renal plasma flow. Lipid solubility and ph do not affect glomerular filtration of drugs. Only non protein bound (i. e. free) drugs are filtered at the glomerulus. Drugs not filtered by the glomerulus leave the glomerulus by the efferent arteriole. The efferent arterioles divide to form capillaries that surround the proximal tubule.