Acetaminophen overdosage, which can cause hepatic failure and death, continues to be a concern. Dozens of over-the-counter combination products contain various doses of the drug. In 2011, the FDA limited the quantity of acetaminophen in prescription products, mostly combinations of acetaminophen and opioids, to 325 mg per dose unit, and Johnson and Johnson, the manufacturer of Tylenol, lowered the maximum dosage of single-ingredient Extra Strength Tylenol from 8 tablets (4000 mg) to 6 tablets (3000 mg) per day and increased the dosage interval from 4-6 hours to 6 hours. Now Johnson and Johnson is adding a warning in red letters to the cap of each new bottle of Extra Strength Tylenol: CONTAINS ACETAMINOPHEN ALWAYS READ THE LABEL.
Single-ingredient acetaminophen tablets sold in large-chain pharmacies are almost invariably “extra strength” (500 mg) rather than “regular strength” (325 mg), despite the fact that there are no published data showing that a dose of 1000 mg is more effective than 650 mg in treating common causes of pain such as headache or osteoarthritis. Some studies have found the higher dose more effective in treating postoperative pain.
At doses of 3000 mg per day in healthy people, acetaminophen has virtually no adverse effects. At 4000 mg per day, serum transaminase elevations can occur. Chronic heavy consumption of alcohol may lower the threshold for acetaminophen-induced liver damage. Severe liver injury has been reported in alcoholics who claimed to have taken less than 4 g of acetaminophen per day, and fatal hepatic injury has been reported in patients who took 4-10 g of acetaminophen per day and claimed to drink only moderate amounts of alcohol.
The moral of this story is that most patients taking acetaminophen for non-operative causes of pain should take regular-strength acetaminophen, if they can find any on the shelves of their pharmacies. Extra-strength acetaminophen is generally unnecessary, and it can be dangerous.