The 10 Most Important Things to Know About Acetaminophen (Tylenol)

Dr. Sharon Orrange
Dr. Orrange is an Associate Professor of Clinical Medicine in the Division of Geriatric, Hospitalist and General Internal Medicine at the Keck School of Medicine of USC.
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Is acetaminophen (Tylenol) a wolf in sheep’s clothing?

For a medication so widely available and so effective, there is a dark side to acetaminophen. Here are 10 things about acetaminophen that may shock you:

1.  Many underestimate its toxicity. In a recent survey of 500 people, 46% reported ingesting excessive amounts because they misunderstood dosing directions or failed to recognize that acetaminophen is found in more than one medication they are using. Yipes.

2.  Half the episodes of acute liver failure in the United States are because of acetaminophen toxicity. Half.

3.  The therapeutic dose (the “safe” dose) of acetaminophen in adults is 325 to 1000 mg given every 4-6 hours with a maximum daily dose of 4 grams in adults.

4.  Toxicity is likely to occur with doses above 12 grams in 24 hours.

5.  Toxicity is less likely to occur with a dose < 10 grams in 24 hours or a single dose less than 7.5 grams in an adult.

6.  Use of other medications along with acetaminophen increase your risk of toxicity. These include Dilantin, isoniazid, rifampin, and Bactrim (sulfamethoxazole/trimethoprim) among others.

7.  KNOW if your pain medication contains acetaminophen. A good clue is that it ends in cet (for acetaminophen) like Ultracet (tramadol/acetaminophen), Roxicet (oxycodone/acetaminophen), Percocet (oxycodone/acetaminophen), Fioricet (butalbital/acetaminophen/caffeine). Others like Vicodin (hydrocodone/acetaminophen), Esgic (butalbital/acetaminophen/caffeine), etc don’t have the easy clue ending but do contain acetaminophen. Know this.

8.  Early symptoms of overdose may be nausea, vomiting, fatigue, and sweating, but some folks may have no symptoms early on.

9.  Liver abnormalities peak 72 to 96 hours after ingestion. This is the stage where most deaths occur (from liver and kidney failure).

10.  In 2011, the FDA put limits on the amount of acetaminophen that could be found in pain meds. Currently, prescription pain meds can include no more than 325 mg of acetaminophen in each tablet or capsule, and existing prescription meds with more than 325 mg of acetaminophen must be removed from the market by January 2014.

Dr O.

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