What is acetaminophen and how does it work?

Acetaminophen is a pain reliever and fever reducer that is an active ingredient in many over-the-counter (OTC) and prescription (Rx) medicines, including not only pain relievers and fever reducers but also medicines for cough, cold, allergy and sleep aids. It was first marketed in the United States in 1953 and has become one of the most popular and widely used medicines.  Because there are hundreds of products available to help manage pain and fever symptoms, my patients often tell me that they are confused about which medicine might be best to treat their own or a family member’s symptoms.

Other OTC medicines for pain and fever relief contain active ingredients that belong to a class of medications known as “non-steroidal anti-inflammatory drugs” or NSAIDs. These include medicines such as ibuprofen, aspirin, and naproxen.

They all work in a similar manner, decreasing pain by reducing inflammation. Acetaminophen, however, is very different. It is not an anti-inflammatory drug but works by blocking pain perception signals in the brain. Some people find that either acetaminophen or NSAIDs work better for their pain. I recommend to my patients that they try them both separately as directed on the Drug Facts label and compare the results.

The body breaks down acetaminophen differently than other pain relievers. The liver is primarily responsible for removing the drug from the body, but in cases of overdose, the liver can become injured. Although acetaminophen is well tolerated by most people at safe doses (and has few drug interactions), overdoses can be very dangerous, and in extreme cases can result in liver failure or death.

I encourage my patients to read all the Drug Facts labels on their OTC medicines and the information that comes with their prescription medicines before they take them. Over 600 medicines including prescription and OTC products contain acetaminophen in the active ingredient list.

What is the recommended dosing of acetaminophen?

It’s important for parents to know that the makers of these medicines have made changes to single-ingredient liquid infants’ and children’s acetaminophen to make it easier for parents and caregivers to use these medicines and to reduce potential medication errors. The medicines are now made in only one strength (as opposed to the three different strengths previously available) and have age-appropriate dosing directions and devices with each package. I encourage you to learn more about the changes and educate yourself on how to determine if the medicine in your home or that you are purchasing contains the old or new concentration.

For infants younger than two years of age, parents and caregivers must consult their healthcare provider for dosing instructions  The Drug Facts label on the packaging of infant’s acetaminophen does not include dosing instructions for this age group.

For children between the ages of 2 through 11, dosing is age or weight-based.  Generally, the recommendations are: 10-15 mg/kg/dose every four to six hours as needed, not to exceed five doses (2.6 g) in 24 hours.

For children 12 and older and adults, “regular release” oral formulations recommend 325-650 mg every four to six hours or 1000 mg three to four times daily (maximum: 4 g daily). While “extended release” oral formulations should be limited to 1300 mg every eight hours (maximum: 3.9 g daily).

For seniors (adults over age 65), the official FDA recommendation is the same as for adult dosing, with a maximum safe limit of 4g of acetaminophen per day. However, some physicians feel that since older adults may be slower to break down the drug in their livers, a 3 g per day limit is prudent. In my opinion, it is always best to take the smallest effective dose. So if a lower dose of acetaminophen manages your pain or fever symptoms adequately, there is no need to take more of it.

Are there certain people who should not take acetaminophen?

Although acetaminophen is well tolerated by most people, those who have liver damage or end-stage kidney disease should ask their doctors if it is safe for them to use it. Acetaminophen may interact with certain seizure medications so those with seizure disorders should also check with their doctors before using acetaminophen. In rare cases, people may be allergic to acetaminophen and should not take it if a severe rash develops.

How can I ensure my family uses acetaminophen safely?

My top tips for safe acetaminophen storage include:

• Keep acetaminophen in its original bottles. The medicine can be affected by moisture and extremes in temperature. Product quality can only be assured if it is stored in its original containers as directed.
• Check the expiration dates. Safely dispose of all expired acetaminophen to ensure a safe and effective product. Check the Drug Facts label on your medicine packaging. Acetaminophen may be one of several active ingredients in multiple different products. Avoid accidental overdose.
• Use the approved dose cups/syringes to insure proper dosing for babies and children. Never “guestimate” your doses.
• Keep acetaminophen up and away and out of the sight and reach of children, stored in a locked drawer or in a high cabinet that they cannot access. Do not leave acetaminophen in your purse or coat pockets. Learn more tips on how to childproof your home and medicine cabinet.