Why is phenacetin banned?

Phenacetin, a painkiller, was the world’s first synthetic pharmaceutical drug. It was one of the first painkillers that was not derived from opium while at the same time being absent of anti-inflammatory qualities. Phenacetin was developed in 1878 by an American chemist, Harmon Northrop Morse. It was introduced into the pharmaceutical market in 1887.

However, it was withdrawn in 1983 in the United States due to unacceptable levels of interstitial nephritis in patients and potential risks of tumorigenicity. Like the United States, most Western countries did not ban phenacetin from being used in marketing until 1983. Phenacetin is a component of APC (aspirin-phenacetin-caffeine).

Possible exposure routes of phenacetin are oral and inhalation. Phenacetin is harmful if swallowed or inhaled and may cause kidney, liver, and blood disorders. It may cause methemoglobinemia and hemolytic anemia due to acute toxicities, but more commonly, as a result of chronic overdosage. A therapeutic plasma level was less than 20 μg ml−1, with 50–150 μg ml−1 being toxic plasma levels in humans. Phenacetin is group 2A (reasonably anticipated to be a human carcinogen) based on sufficient evidence of carcinogenicity in experimental animals, according to the IARC Working Group.

Phenacetin is banned worldwide primarily due to its proven renal toxicity and classification as a Group 1 carcinogen by the IARC.

Long-term or high-dose use causes analgesic nephropathy, characterized by renal papillary necrosis, leading to chronic kidney failure, end-stage renal disease, and an elevated risk of urothelial cancers (e.g., renal pelvis, bladder, ureter). Its active metabolite p-phenetidine is key to these toxic effects. Additionally, it may induce acute hemolysis in people with G6PD deficiency.

First marketed in 1887, it was withdrawn from the U.S. market in 1983 and banned in most countries, as safer alternatives like paracetamol (acetaminophen) became available.

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