Analgesic nephropathy is one type of toxic injury to the kidney. It is usually a result of prolonged or chronic ingestion of analgesics, especially over-the-counter (OTC) medications that contain phenacetin or acetaminophen and nonsteroidal antiinflammatory drugs (NSAIDs) including aspirin or ibuprofen. The ingestion may have been excessive, with as much as 4 to 5 pounds of total medication ingested over a period of years, or about 3 pills per day for 6 years. This frequently occurs as a result of self-medication, often for some type of chronic pain. Analgesic nephropathy occurs in about 4 out of 100,000 people, mostly women over 30. The rate has decreased significantly since phenacetin is no longer widely available in OTC preparations. Risk factors include use of OTC analgesics containing more than one active ingredient, chronic headache, chronic backache or musculoskeletal pain, pain with menstrual periods, emotional and/or behavioral changes, and history of dependent behaviors including smoking, alcoholism, and excessive use of tranquilizers. There may also have been a history of the following conditions: The damage occurs within the internal structures of the kidney. There is interstitial nephritis and renal papillary necrosis, eventually leading to acute renal failure or chronic renal failure. The tissue of the kidney may slough off into the urine. There may be blood and pus in the urine, with or without positive urine cultures or other signs of infection, and there may be minimal or no loss of protein in the urine.
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