Which medical conditions and medications are contraindicated for acetaminophen?
Jun 25, 2019 • 3 comments
Acetaminophen is a widely used drug. Used under normal conditions, it is safe and effective, but are you aware of the common drug interactions and diseases for which it is contraindicated?
Read our guide to learn more.
What is acetaminophen?
Acetaminophen (aka paracetamol) is the most widely sold drug in the UK. Acetaminophen is the active substance of a number of analgesic drugs, i.e. mild to moderate pain relieve. It can also be used for fevers.
Acetaminophen is a safe and effective drug when used under normal conditions and, therefore, can be used in children, pregnant women, or breastfeeding women.
When and how to take acetaminophen?
For an adult over 110 lbs, the maximum recommended dose of acetaminophen is 3 grams per 24 hours. This corresponds to 3, 1000 mg tablets per day (1000 mg = 1 g). In cases of more severe pain and with the advice of a doctor, the maximum dose may be 4 grams per day, not for a prolonged duration of time.
In both cases, acetaminophen doses should be at least 4 hours apart, with idealy 6 hours between doses. Be careful, in some cases, the maximum dose and duration between doses may change. These cases are explained below in the article. The most effective dose of acetaminophen remains, as with many drugs, the lowest dose for the shortest period of time.
If acetaminophen is used for acute pain and the pain persists after 5 days of treatment, it is recommended to seek medical advice. In the case of a fever, if after 3 days of treatment with acetaminophen there is no improvement in symptoms or there is an increase in symptoms, a consultation with a doctor is recommend.
What medications contain acetaminophen?
There are many medication brands that contain acetaminophen. In some cases, it is combined with other medications.
It is recommended to avoid combining two drugs that contain acetaminophen or, if that is not possible, not to exceed the maximum dose of 3 grams per 24 hours.
Here is a list of the main drugs containing paracetamol:
Over the counter drugs (OTC) containing only acetaminophen
OTC medications containing acetaminophen in combination with other medications:
- Goody's® Powders
Prescription drugs containing acetaminophen in combination with other medications
- Tylenol® with Codeine
What conditions may be contraindicated for acetaminophen ?
In the case of renal failure, it is recommended to leave an interval of 8 hours between doses of acetaminophen and not exceed 3g per 24 hours.
Severe liver failure is an absolute contraindication to the use of acetaminophen. Indeed, its elimination depends on the liver, so when the liver does not function effeciently, acetaminophen cannot be eliminated properly.
In cases of mild to moderate hepatic insufficiency, it is advisable to limit the consumption of acetaminophen to 2 to 3 grams per 24 hours and to use it only for short periods of time, while always remaining cautious. Consult your doctor if you have any doubts!
What drugs may be contraindicated for acetaminophen?
Anticoagulants (aka blood thinners, aka vitamin K antagonists): Coumadine®, Heparin®, Eliquis®, Warfarin
When taking acetaminophen with anticoagulants, caution should be exercised. 4g of acetaminophen per day for at least 4 days, enlarges the risk of an increase in the effect of anticoagulants - an increase in the risk of bleeding.
In this case, biological monitoring by INR measurement should be performed during and at the end of acetaminophen treatment.
Bile acid chelating resins: Questran®, Colestid®, Welchol®, Colesevelam, Cholestyramine
As these medications can cause poor intestinal absorption of acetaminophen, it is advisable to take both drugs at least 2 hours apart.
When acetaminophenis eliminated by the liver, a small part is transformed into a toxic product for the liver. In case of acetaminophen overdose, there is a significant increase in toxic metabolites. Acetaminophen overdose is defined as the consumption of more than 6 grams of acetaminophen per day.
An overdose can lead to severe liver toxicity and acute hepatitis. This toxicity may also be increased when certain drugs are taken at the same time as acetaminophen.
Here are some medications that may increase liver toxicity:
Some anti-epileptic drugs:
- Phenobarbital (Luminal®, Solfoton®)
- Gabapentin (Neurontin®)
- Phenytoin (Dilantin®, Phenytek®)
- Carbamazepine (Tegretol®)
Antibiotic Rifampicin (Rifadine®, Rimactane®)
If you regularly take acetaminophen without a prescription to relieve pain, do not hesitate to discuss it with your doctor, who may be able to offer you other or more appropriate solutions for pain relief.
How often do you use acetaminophen? Did you know about these contraindications?