Phenacetin hemolytic anemia with

Variations on the molecular structures have provided improved side effect profiles of agents used. For example, although phenacetin and acetaminophen are not anti-inflammatory agents, they are included in this chapter, because they are analgesics and antipyretics and illustrate the point that improvement in molecular structure from phenacetin to acetaminophen helped to reduce the hepatotoxicity and risk for drug-induced hemolytic anemia with which phenacetin was associated when it was on the market in the past. 

Hemolytic anemia and methemoglobinemia are very rare adverse events. Interstitial nephritis and papillary necrosis—serious complications of phenacetin—have not occurred nor has gastrointestinal bleeding. Caution is necessary in patients with any type of liver disease. 

Hemolytic anemia and methemoglobinemia, reported with the use of phenacetin, are rarely noted with acetaminophen. Interstitial nephritis and papillary necrosis—serious complications of phenacetin—although anticipated with widespread chronic use of acetaminophen, have not occurred. Gastrointestinal bleeding does not occur. Caution should be exercised in patients with liver disease. 

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 pg ml with 50-150 pg ml being toxic plasma levels in humans. 

Drug-dependent antibodies causing IMHA have been found in AIDS patients (Gonzalez et al, 2003). Other cases of IMHA after the administration of tei-coplanin, a glycopeptide antibiotic (Coluccio et al., 2004) and by a metabolite of etodolac, a nonsteroidal anti-inflammatory drug (Cunha et al., 2000), have also been reported. Hemolytic anemia associated with antibodies to older drugs like tolbutamide and phenacetin have been known for decades (Bird et al.,1972). 

It is an analgesic and an antipyretic with similar effectiveness as aspirin. It has a greater potential for toxieity (hemolytic anemia and methemoglobinemia) than paracetamol. Irreversible kidney damage with prolonged ingestion of phenacetin has been established whieh ultimately resulted in complete withdrawal of this drug in many countries. 

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