Paracetamol Drug Interactions

Paracetamol can interact with certain other drugs and medications and cause serious harm. Patients who are using Paracetamol should never use alcohol while taking their medication in order to avoid damage to the liver. There are dozens of over-the-counter medications that contain acetaminophen such as Tylenol; these should all be avoided in order to prevent accidental overdose. Some prescription pain medications including Lortab and Percocet also contain the same active ingredients as Panadol and should be avoided.

Since paracetamol is processed in the liver, medications and substances that affect liver enzymes can likely cause drug interaction when taken with paracetamol. Combining paracetamol with these drugs can lead to liver problems.

Discuss with your healthcare provider all drugs (both prescription and non-prescription) that you currently and normally take to prevent possible drug interactions.

Significant Drug Interactions

Some drugs that can cause significant drug interaction when taken with paracetamol include:

Anticonvulsant drugs – People chronically treated with anticonvulsants, who overdose on paracetamol, are at increased risk of liver damage because of the increased metabolism of paracetamol. Furthermore, anticonvulsants particularly barbiturates makes the paracetamol less effective and more toxic. Caution should be taken when combining these drugs.

• Amobarbital (Amytal)
• Butalbital (Fioricet, Fiorinal)
• Pentobarbital (Nembutal)
• Phenobarbital (Luminal)
• Secobarbital (Seconal)
• Carbamazepine (Carbatrol, Epitol, Tegretol)

Certain non-narcotic analgesic – Diflunisal (a non-narcotic analgesic) increases the plasma levels of paracetamol by approximately 50%. Although the clinical significance of this increase is still unclear, caution should be taken when using these drugs together.

• Diflunisal (Dolobid)

Certain antibiotics – Chronic use of isoniazid, an antibiotic drug often prescribed for tuberculosis, may increase the risk of liver damage when combined with paracetamol even at recommended “safe” doses.

• Isoniazid (Laniazid, Nydrazid)

Oral anticoagulants (blood thinners) – Paracetamol can possibly potentiate the effects of blood thinners, increasing the risk of bleeding. However, the risk is comparably less than other over-the-counter pain relievers (such as aspirin). It is important to monitor for signs of bleeding as well as regular diagnostic test, specifically international normalized ratio (INR) or prothrombin time, when taking paracetamol while on anticoagulant therapy.

Paracetamol doses more than 2275 mg per day may potentiate the effect of warfarin. Therefore, patients on warfarin therapy should avoid prolonged use of high dose paracetamol.

• Warfarin (Coumadin, Jantoven)

Certain cholesterol-lowering agents – Cholestyramine, a bile acid sequestrant used for reducing blood cholesterol, binds with acetaminophen thereby preventing it from being absorbed by the body. Cholestyramine reduces the desired pharmacologic effect of paracetamol. If taking these medications together, acetaminophen should be taken at least 1 hour before cholestyramine, or at least 3 to 4 hours after cholestyramine.

• Cholestyramine (Prevalite, Questran)

Other medications that contain paracetamol/acetaminophen - Concomitant use of different drugs that contain paracetamol increases the risk of side effects as well as drug overdose. Take note that there are various drugs that contain paracetamol. Be sure to discuss with your healthcare provider use of such drugs before taking paracetamol.

• Many pain relievers
  • Codeine and acetaminophen (e.g. Tylagesic)
  • Tramadol and acetaminophen (e.g. Ultracet)
  • Propoxyphene and acetaminophen (e.g. Balacet 325, Darvocet)
  • Oxycodone and acetaminophen (e.g. Endocet, Narvox)
• Many over-the-counter cough-and-cold, flu, and allergy medications
• Many over-the-counter menstrual medications (e.g. Midol)