Analgesic nephropathy involves damage to one or both kidneys caused by overexposure to mixtures of medications, especially over-the-counter pain remedies (analgesics).

Analgesic nephropathy involves damage within the internal structures of the kidney. It is caused by long-term use of analgesics, especially over-the-counter (OTC) medications that contain phenacetin or acetaminophen and nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin or ibuprofen.

The excessive use may equal about three pills per day for 6 years. This frequently occurs as a result of self-medicating, 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
• Emotional or behavioral changes
• History of dependent behaviors including smoking, alcoholism, and excessive use of tranquilizers
• Pain with menstrual periods

Persons with this condition may also have a history of the following conditions:

• Urinary tract infections (see acute UTI)
• Interstitial nephritis
• Renal calculi
• Prerenal azotemia
• Congestive heart failure
• Blood volume depletion (such as dehydration)

• Weakness
• Fatigue
• Increased urinary frequency or urgency
• Blood in the urine
• Flank pain or back pain, renal colic (occasional)
• Decreased urine output
• Decreased alertness
  • Drowsiness
  • Confusion, delirium
  • Lethargy
• Decreased sensation, numbness (especially of extremities)
• Nausea, vomiting
• Easy bruising or bleeding
• Swelling, generalized

A physical examination may show signs of interstitial nephritis or kidney failure.

Blood pressure may be high. The doctor may hear abnormal heart or lung sounds when listening to the chest with a stethoscope. There may be signs of premature skin aging.

Lab tests may show blood and pus in the urine, with or without signs of infection. There may be mild or no loss of protein in the urine.

Tests that may be done include:

• Complete blood count
• Examination of sediment or tissue passed in the urine
• Intravenous pyelogram (IVP)
• Toxicology screen
• Urinalysis