8 Acetaminophen Interactions You Should Know About

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Acetaminophen (Tylenol) is the most commonly used pain medication in the world. Along with treating mild pain, it can also help reduce a fever.

Even though acetaminophen is available over the counter (OTC), it can still have drug interactions. Some acetaminophen reactions may be mild. But others can be more serious and may require you to avoid acetaminophen altogether.

Below, we'll discuss eight acetaminophen interactions that you should know about. But keep in mind, this doesn't cover all possible acetaminophen interactions. So talk to your prescriber or pharmacist before taking medication that contains acetaminophen. They can help you check for interactions.

1. Other acetaminophen-containing medications

Acetaminophen is a common ingredient in many OTC medications. This includes combination cold medications like NyQuil Cold & Flu (acetaminophen / dextromethorphan / doxylamine. Some pain medications, like Excedrin Migraine (acetaminophen / aspirin / caffeine) and Midol Complete (acetaminophen / caffeine / pyrilamine), also contain acetaminophen.

Because acetaminophen is in so many OTC products, it can be tricky to make sure you're not taking too much.

Taking large amounts of acetaminophen can increase your risk of liver damage. It can also lead to acetaminophen overdose. Mild side effects of acetaminophen overdose may include nausea, vomiting, or constipation. In severe cases, overdose can cause organ damage, confusion, and even death.

The safe maximum dose of acetaminophen for most adults is 4,000 mg per day. But if you're taking acetaminophen for more than 7 days in a row, a maximum dose of 3,250 mg per day may be safer. And in some situations, like in people with a history of liver problems, an even lower acetaminophen dose is best.

To avoid taking too much acetaminophen, make sure you're reading medication labels. If you're not sure whether a medication contains acetaminophen, talk to your pharmacist. They'll be able to look at your medication list and let you know.

2. Alcohol

If you drink alcohol, you may know about the effects it can have on your body. It can affect almost every organ - including the brain, heart, and kidneys. Excessive alcohol use can also cause liver damage. Similarly, too much acetaminophen can also cause liver damage.

Safe amounts of alcohol and acetaminophen aren't usually damaging to your liver. If you drink alcohol, it's recommended to limit alcoholic drinks to 1 drink per day in women and 2 drinks per day in men. The recommended acetaminophen doses are discussed above.

Although having the occasional drink while taking acetaminophen is likely OK, talk to a healthcare professional (HCP) if you drink above the recommended amount of alcohol. The interaction between acetaminophen and alcohol becomes more dangerous if you take too much of either substance. To prevent liver damage, aim to take as little acetaminophen as possible. And make sure you're drinking less alcohol than the recommended amount.

3. Medications that increase acetaminophen levels

Some medications can affect the way the body metabolizes (breaks down) acetaminophen. These medications may cause higher levels of acetaminophen. This makes side effects more likely.

Examples of medications that can increase the risk of side effects from acetaminophen include phenobarbital, phenytoin (Dilantin), and carbamazepine (Tegretol).

These medications may make liver damage from acetaminophen more likely. Before starting acetaminophen, talk to an HCP or pharmacist. They can help you find out if you take a medication that interacts with acetaminophen. They'll let you know if you need a lower dose of acetaminophen or if it should be avoided altogether.

4. Warfarin

Warfarin (Jantoven) is an oral anticoagulant. These medications, also known as blood thinners, are used to prevent and treat blood clots. Abnormal blood clotting can lead to stroke or heart attack.

Acetaminophen may amplify the effects of warfarin, which can raise your risk of side effects like bleeding. If you're taking warfarin, your HCP will check a blood test called the international normalized ratio (INR) periodically. Your INR is a test that checks how long it takes for your blood to clot. Acetaminophen may increase your INR. So you may need to have it checked more often if you're taking warfarin and acetaminophen together. If you take acetaminophen regularly, it's possible that your HCP will recommend a dose adjustment for warfarin.

It's important to note that acetaminophen and other blood thinners aren't known to interact. This includes rivaroxaban (Xarelto), apixaban (Eliquis), and dabigatran (Pradaxa).

5. Isoniazid

Isoniazid is a medication that treats and prevents tuberculosis. It makes several enzymes (proteins) that metabolize acetaminophen more active. This can cause acetaminophen to metabolize into a toxic chemical. And this raises your risk of liver damage.

If you take isoniazid, talk to a HCP before taking acetaminophen. They may want you to avoid acetaminophen completely. They might be able to suggest another OTC pain reliever if you need pain relief.

6. Rifampin

Rifampin (Rifadin) is a medication that treats tuberculosis, a bacterial infection that affects the lungs. It can also prevent the spread of other types of infections like meningococcal disease. Like isoniazid, rifampin may cause acetaminophen to metabolize into a toxic chemical that can hurt the liver.

Even though there is little research on how significant this interaction is, it may be best to avoid taking rifampin and acetaminophen at the same time. So if you take rifampin, talk to your HCP about which pain relievers are safe to use.

7. Cholestyramine

Cholestyramine (Prevalite, Locholest) is a cholesterol-lowering medication. It may also be taken to relieve itching from conditions that block the bile duct. Cholestyramine works by attaching to bile acid in the body. But cholestyramine can also attach to many medications, including acetaminophen. This affects how well it's absorbed (especially if they're taken at the same time).

If you take cholestyramine, you may need to take it at least 1 hour after acetaminophen to decrease chances of this interaction.

8. Childhood vaccines

It's generally recommended toavoid giving acetaminophen before your child's vaccine. This is true of other fever-reducers, like ibuprofen, too. Below, we'll explain why this recommendation exists.

Vaccines are a way to protect against serious infections and illnesses. They work by causing an immune response to a particular disease-causing bacteria or virus before your body comes into contact with it. Some studies havecalled into question whether taking acetaminophen before getting a childhood vaccinelowers your immune response. This would make vaccines less effective.

But the research is mixed. So it's not clear just how significant of an effect acetaminophen has on vaccine efficacy. Although acetaminophen and other pain relievers maytemporarily lower the immune response when given before vaccines, it's not clear if this impacts how well the vaccine works. Since the research isn't clear, the recommendation is to avoid acetaminophen and other fever-reducers before vaccine administration in most cases.

If your child takes acetaminophen on a regular basis, talk to their HCP about whether you should avoid administering it before their next vaccine. Their HCP may still suggest continuing it if the benefit outweighs the potential risk.

Acetaminophen Interaction FAQs

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