Phenacetin

Phenacetin, introduced in 1887, is used principally as an analgesic. Typical doses of 300mg to 500mg a day result in an analgesic effect. Its analgesic effects are due to its actions on the sensory tracts of the spinal cord. In addition, phenacetin has a depressant action of the heart, where it acts as a negative inotrope. It also is an antipyretic, acting on the brain to decrease the temperature set point. It is also used to treat rheumatoid arthritis (subacute type), intercostal neuralgia, and some forms of ataxia.

Phenacetin, and products containing phenacetin have been shown in an animal model to be carcinogenic. In humans, many case reports have implicated products containing phenacetin in urothelial neoplasms, especially transitional cell carcinoma of the renal pelvis. In one prospective series, phenacetin was associated with an increased risk of death due to urologic or renal diseases, death due to cancers, and death due to cardiovascular diseases. In addition, people with glucose-6-phosphate dehydrogenase deficiency may experience acute haemolsis while taking this drug.

The most popular brand of phenacetin was Roche's Saridon. Due to its carcinogenic properties and a link to analgesic-induced nephropathy, Saridon was reformulated in 1983. The new formulation contains propyphenazone, paracetamol and caffeine. Both propyphenazone and paracetamol are metabolites of phenacetin with similar analgesic and antipyretic effects. The new formulation has not been shown to share phenacetin's carcinogenic side-effects.

Connection between chronic phenacetin use and renal papillary necrosis

Chronic use of phenacetin is known to lead to renal papillary necrosis.

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