Acetaminophen: Curbing Overdose and Liver Toxicity

Roni Shye
Roni Shye, PharmD BCGP BCACP, is a licensed pharmacist in the states of Florida, Ohio, and Pennsylvania.
Posted on

Acetaminophen (Tylenol) toxicity has become more of an issue, especially due to the rise of combination products. These include prescription pain medications (such as hydrocodone/acetaminophen, oxycodone/acetaminophen, butalbital/acetaminophen, acetaminophen/codeine and tramadol/acetaminophen) in which acetaminophen is used as a second pain reliever. It is also widely available over the counter, and many over-the-counter combinations that advertise pain or fever relief contain acetaminophen as well.

The FDA is on the case:

The Food and Drug Administration (FDA) is requiring manufacturers to limit the amount of acetaminophen to 325 mg in prescription drugs by January 14, 2014. This is intended to reduce the risk of accidental overdose and liver injury. The FDA is also requiring a boxed warning to highlight the potential for liver injury. The new rule will affect all prescription medications, but it doesn’t affect over-the-counter drugs.

These changes are already beginning to take effect, and reformulated versions of some prescriptions including Vicodin (hydrocodone/acetaminophen 5 mg/300 mg, 7.5 mg/300 mg, 10 mg/300 mg) are already available. However, these new products will have higher costs and copays, and in some cases may not be covered by your insurance. When a new brand formulation (like Vicodin) is introduced, generics will also need to be reformulated to meet the FDA mandate—this means you may see expensive brands with no generics in some cases. Prescription drugs (brand or generic) with 325 mg of acetaminophen or less will continue to be available.

Why is too much acetaminophen dangerous?

The liver can only metabolize a fixed amount of acetaminophen per day. Once this limit is reached, it causes liver injury and can lead to acute liver failure. Overdose of acetaminophen is the leading cause of acute liver failure in the United States, and around 50% of those cases are accidental. It is estimated that there are over 25,000 hospitalizations due to acetaminophen overdose each year.

How much acetaminophen is too much?

For healthy adults, acetaminophen should be limited to a maximum of 4000 mg per day. In certain individuals, such as the elderly, it should only be 3000 mg. Check with your provider or pharmacist to see what’s right for you. For reference, over-the-counter acetaminophen is typically sold in 325 mg or 650 mg doses; 4000 mg per day would be about twelve 325 mg tablets.

What can you do to prevent overdosing?

You can limit your intake by taking medications as directed, limiting use to an as-needed basis, and calculating your total daily acetaminophen dose. Additionally, if you are taking a prescription med containing acetaminophen, limit the amount of over-the-counter acetaminophen you use. Remember your 4000 mg max per day!

Talk to your health care provider or pharmacist if you have any questions.

Till next time,

The GoodRx Pharmacist

For more information on acetaminophen toxicity, also see Dr. O’s post on The 10 Most Important Things to Know About Acetaminophen

Drugs featured in this story

Filed under