Sunday, January 10, 2010

Analgesic Nephropathy

Analgesic nephropathy is a medical condition in which the kidney does not function properly, with impaired filtering capacity, due to an excessive ingestion of analgesic medications such as aspirin, nimesulide, phenacetin, and paracetamol. Analgesic nephropathy usually refers to damage induced by excessive use of combinations of these medications, especially combinations that include phenacetin, gradually leading to irreversible kidney failure and the permanent need for dialysis or a kidney transplant to restore kidney function. It may also be used to describe kidney injury from any single analgesic medication.

The kidney damage produced by analgesics are renal papillary necrosis and chronic interstitial nephritis. They appear to result from decreased blood flow to the kidney, rapid consumption of antioxidants, and subsequent oxidative damage to the kidney. This kidney damage may lead to abnormal urinalysis results, high blood pressure, and anemia. A small proportion of individuals with analgesic nephropathy may develop end-stage kidney disease.

Analgesic nephropathy was once a common cause of kidney injury and end-stage kidney disease in parts of Europe, Australia, and the United States. The scarring of the small blood vessels, called capillary sclerosis, is the initial lesion of analgesic nephropathy. Found in the renal pelvis, ureter, and capillaries supplying the nephrons, capillary sclerosis is thought to lead to renal papillary necrosis and, in turn, chronic interstitial nephritis. How phenacetin and other analgesics lead to this damage is incompletely understood. It is currently thought that the renal toxicities of NSAIDs and the antipyretics phenacetin and paracetamol may combine to give rise to analgesic nephropathy. A committee of investigators reported in 2000 that there was insufficient evidence to suggest that non-phenacetin analgesics by themselves are associated with analgesic nephropathy.

If someone has been taking analgesics regularly to control chronic pain, he may be advised to find new ways to treat his pain, such as behavior modification or relaxation techniques. Depending on how much his kidney function has declined, he may be advised to change his diet, limit the fluids he drinks, or take medications to avoid anemia and bone problems caused by kidney disease. His doctor will monitor his kidney function with regular urine and blood tests.