Acetaminophen Poisoning
More than 100 products contain acetaminophen, a common over-the-counter pain reliever (see Section 2, Chapter 18). If several similar products are consumed at a time, a person may inadvertently take too much acetaminophen. Many preparations intended for use in children are available in liquid, tablet, and capsule form, and a parent may try several preparations simultaneously or within several hours, not realizing they all contain acetaminophen.
Acetaminophen usually is a very safe drug, but it is not harmless. To cause poisoning, several times the recommended dose of acetaminophen must be taken. For example, a person who weighs 150 pounds generally needs to take at least 20 325-mg tablets before toxic effects due to a single overdose are possible. Death is extremely unlikely unless the person takes more than 40 325-mg tablets. In toxic doses, acetaminophen can damage the liver. Liver failure can follow.
Symptoms and Diagnosis
Most overdoses produce no immediate symptoms. The level of acetaminophen in the blood, measured 2 to 4 hours after ingestion, predicts the severity of the liver damage accurately. If the overdose is very large, symptoms develop in four stages. In stage 1 (after several hours), the person may vomit but does not seem ill. Many people have no symptoms until stage 2 (after 24 hours), when nausea, vomiting, and abdominal pain may develop. At this stage, blood tests show that the liver is functioning abnormally. In stage 3 (after 2 to 5 days), vomiting becomes worse. Tests show that the liver is functioning poorly, and jaundice and bleeding develop. In stage 4 (after 5 days), the person either recovers quickly or experiences liver failure, which may prove fatal.
Treatment
If acetaminophen was taken within the previous several hours, activated charcoal is usually given.
If the level of acetaminophen in the blood is high, acetylcysteine is generally given by mouth or intravenously to reduce the toxicity of the acetaminophen. Acetylcysteine is given repeatedly, for one to several days. Treatment for liver failure may also be necessary.
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