A. At therapeutic doses, acetaminophen is well tolerated; however, untoward effects include:
Skin rash and drug fever (an allergic reaction to the drug).
Rare instances of blood dyscrasias (haemolyticanaemia in with G6PD deficiency, less than with phenacetin).
Renal tubular necrosis and renal failure (more with phenacetin).
B.An overdose of acetaminophen(about 15 gm in an adult; about 4 gm in a child)
can result in severe hepatotoxicity, resulting in centrilobular hepatic necrosis. Doses greater than 20 gm are potentially fatal.
The toxic metabolite of acetaminophen appears to be inactivated in the liver via glutathione.
It is thought that when glutathione stores are consumed, the N-acetyl-p-benzoquinone metabolite binds covalently to cellular constituents, producing Acute hepatocellular damage within one month.
Although clinical symptoms, such as nausea and vomiting, occur during the first 24 hours after toxic ingestion, signs of hepatic damage (e.g. enzyme abnormalities) may not occur for 2 - 6 days).
Treatment consists of:
Emptying the stomach & administering activated charcoal
Hemodialysis last resort, if begun within the first 12 hours after ingestion.
Administration of sulfhydryl compounds (e.g. acetylcysteine) which probably replenish hepatic stores of glutathione.