Acetaminophen

Acetaminophen is used to treat pain associated with osteoarthritis (OA) and, sometimes, inflammatory forms of arthritis.

Acetaminophen is typically taken orally.

The typical dose of acetaminophen is 325 mg to 1,000 mg every four to six hours. The maximum daily dose is usually four grams (4,000 mg) but your healthcare team may recommend a lower maximum dose if you have any liver or kidney issues.

• Regular Strength tablets (325 mg each): One to two tablets every four to six hours to a maximum of 12 tablets per day.

• Extra Strength tablets (500 mg each): One to two tablets every four to six hours to a maximum of eight tablets per day.

• Extended-Release tablets (650 mg each) (i.e., Tylenol® Arthritis, Tylenol® Muscle Aches and Body Pain): One tablet every eight hours to a maximum of six tablets per day.

The mechanism of action of acetaminophen is not well understood. A proposed mechanism is that acetaminophen blocks prostaglandin synthesis by inhibiting COX-1 and COX-2. Prostaglandins control processes of pain and inflammation, by blocking them, acetaminophen provides pain relief. 

Acetaminophen typically begins to take effect within one to two hours.

Ask a doctor or pharmacist before use if you have serious liver or kidney disease or chronic alcohol use (three or more drinks per day). Do not take acetaminophen if you have an allergy to acetaminophen. 

Taking more than the recommended maximum daily amount of acetaminophen can be dangerous. If you have consumed more than the recommended amount, please contact your healthcare provider immediately, even if you do not notice any possible signs or symptoms of excess use, such as increased sweating, nausea, vomiting, stomach pain and loss of appetite. 

Acetaminophen, when taken daily, may interact with warfarin. If you take warfarin for another medical condition, please speak to a healthcare provider before starting regular acetaminophen.

Although acetaminophen is one of the safest medications for treating pain and is generally well tolerated, long-term use carries a low, but dangerous, risk of liver damage and possible kidney damage.

Do not exceed the maximum daily dose of acetaminophen. Acetaminophen is found in a number of other over-the-counter medications, such as cough and cold products and prescription medications for pain relief. Carefully look at the ingredients of all the over-the-counter medications and prescription medications you are taking to ensure you are not taking too much acetaminophen. Consult your pharmacist if you have questions about the amount of acetaminophen in over-the-counter products.

Avoid regular consumption of alcohol while taking acetaminophen as it can increase the risk of liver toxicity. Consuming more than three alcoholic drinks per day may increase the risk of liver damage.

Routine blood tests or monitoring are not normally required while you are taking acetaminophen. Your healthcare provider may meet with you regularly to ensure that acetaminophen is adequately controlling your pain.

Store this medication at room temperature (15 to 30 degrees Celsius) and keep it out of reach of children.