What Drugs Interact With Acetaminophen?
Acetaminophen, commonly known as the brand name Tylenol, is an over-the-counter analgesic pain reliever and fever reducer. It also is included with certain prescription pain relievers, such as codeine, to relieve more severe pain. Acetaminophen relieves pain by raising the body's pain threshold, and reduces fever by acting on the heat-regulating area of the brain. Acetaminophen interacts with several drugs, but generally is very safe.
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Alcohol and Isoniazid
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Acetaminophen affects the liver and can cause liver dysfunction, especially when taken in high doses and for long periods of time. Product labeling advises consumers to consider avoiding acetaminophen use if they drink three or more alcoholic beverages each day, because alcohol also affects the liver. Additionally, the antibiotic isoniazid can cause liver dysfunction, and people taking this drug should avoid using acetaminophen.
Decreased Absorption and Action
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Cholestyramine (Questran) decreases the body's absorption of acetaminophen by the intestine, so the patient should take acetaminophen at least three hours after or one hour before taking cholestyramine. Additionally, drugs that increase the action of liver enzymes that metabolize acetaminophen decrease acetaminophen levels. These include carbamazepine, isoniazid and rifampin. Barbiturates also affect the way the body processes acetaminophen, which can make both medications less effective and more hazardous.
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Increased Levels
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Diflunisal (Dolobid), a non-steroidal anti-inflammatory drug (NSAID), also interacts with acetaminophen. It has been shown to increase plasma concentrations of acetaminophen by as much as 50 percent, according to Dolobid labeling.
Anticoagulants
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Taking large doses of acetaminophen or using it on a long-term basis may increase the effects of anticoagulants such as warfarin (Coumadin). This can lead to increased bleeding. However, the risk is less with acetaminophen than it is with aspirin or other NSAIDs.
Acetaminophen-Containing Medicines
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Patients should be aware that many over-the-counter medications contain acetaminophen. If these are used along with Tylenol or a generic form of acetaminophen, the acetaminophen dosage can be significantly increased. Acetaminophen is found in certain cough, cold and allergy products, as well as many medications that provide relief for menstrual pain.
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