Acetaminophen

The first line medication to treat mild to moderate acute pain is acetaminophen (Tylenol). It is generally well tolerated, has few drug-drug interactions, doesn’t raise blood pressure, can be used during pregnancy and is the drug of choice with impaired kidney function. It is also inexpensive.

The side effect profile for acetaminophen is exceedingly good, but there is a relatively narrow therapeutic window (the difference between a therapeutic dose and a toxic dose). The main toxicity, hepatic injury, is a serious concern. Until recently, the maximum daily dose of acetaminophen was 4000 mg daily (12 regular strength Tylenol). Since acetaminophen is in so many over the counter medications there is increasing concerns about unintentional overdose. Government regulators suggest that the maximum dose should be 2600 mg per day (8 regular strength pills).

Although the drug is remarkably safe when taken at usual therapeutic doses, overdose of acetaminophen   has been recognized since 1966 to cause fatal and nonfatal permanent liver damage. It is suspected that even repeated therapeutic or slightly excessive doses can be hepatotoxic in susceptible individuals, such as alcoholics. Acetaminophen poisoning has become the most common cause of acute liver failure in the United States.  

Patients who are older and malnourished appear to be at increased risk for acetaminophen toxicity. Smoking may also be a risk factor. Acetaminophen should not be taken on an empty stomach. 

The most important advice is to carefully read the label of all over the counter medications. Acetaminophen is a component of hundreds of over-the-counter and prescription medications used worldwide. Many patients ingest excessive amounts of acetaminophen because they misunderstand dosing directions or fail to recognize that acetaminophen is found in more than one medication they are using. 

Acetaminophen is a valuable medication but it must be respected as much as any prescription product.