The incidence of renal impairment increases significantly with age. Because many drugs are eliminated primarily in urine, clearance of these drugs will be impacted greatly with renal dysfunction. The effects of renal impairment are not always clear-cut. For example, clearance of morphine in patients with renal impairment is affected only to a modest degree. However, clearance of the conjugated metabolites, morphine-6-glucuronide and morphine-3-glucuronide, is reduced dramatically. Accumulation of the glucuronide metabolites in patients with renal impairment is associated with respiratory depression, sedation, nausea, and vomiting.
Congestive heart failure, liver cirrhosis, and nephrotic syndrome are diseases that cause edema, which affects renal blood flow.
Conditions or substances that affect the pH of urine affect the rate of excretion.
The degree of protein binding of the drug also affects the rate of elimination.
Glomerular filtration and tubule function is not fully developed in the neonate.
Renal impairment slows the rate of excretion and prolongs the effects of the drug.
