Drug Facts for Africans: Acetaminophen

By: Ruth Abi, B. Pharm. Freelance Health Writer and Datelinehealth Africa Volunteer.  Review by; Chinedu Akpa. B. Pharm.

Bottle of acetaminophen (paracetamol) tablets

• Drug name: Acetaminophen (Paracetamol)
• Drug class: Analgesic (Pain killer)
• Dosage forms: Tablets, caplets, injection, syrup, suppositories, infusion

Before you write off this information because you think it is “just” acetaminophen (paracetamol), did you know that exceeding the prescribed dose of pain medications like paracetamol has a serious adverse effect of liver toxicity? Now that I have your attention, let’s get started!

That a drug is commonly used does not change the fact that it is a drug. Paracelsus says it perfectly: “All drugs are poisons, the benefit depends on the dosage.”

The purpose of this article is to educate readers on the appropriate use of common pain medications like acetaminophen.

What is acetaminophen?

Acetaminophen is a pain reliever and helps to relieve fever. It is used in the treatment of mild to moderate pain. In severe pain, it is used with stronger pain killers called opioids. Some conditions acetaminophen is capable of treating include: headaches, body aches, toothache, menstrual cramps, sore throat and fever. [1]

How does acetaminophen work?

It was formerly believed that acetaminophen relieves pain by inhibiting an enzyme called cyclooxygenase (COX). But, current research suggests that acetaminophen gets converted into a chemical called N-acetylphenolamine (AM404). AM404 then interacts with two receptor sites in the brain:

(i)   Transient receptor potential vaniloid 1 (TRPV1)

(ii)   Cannabinoid 1 (CB1)

Receptors are like sensory organs in the cell membrane. They bind to specific substances outside the cell membrane and cause specific effects in the cell.

Asides its activity on the brain, acetaminophen also acts on the spinal cord. Acetaminophen is not effective against inflammation because its inhibition of cyclooxygenase is weak. [2]

How should I take acetaminophen?

Acetaminophen should be taken as written on the label, or as prescribed by a physician.

• Adults and kids above 12 years old: 500mg to 1g tablet or caplet every 4 to 6 hours, with a maximum of 4g (8) daily when taken by mouth.

For kids less than 12 years old, a syrup is mostly used orally.

• Kids aged 3 to 6 months: 60mg up to four times daily.

• 6 months to 2 years: 120mg up to four times daily.

• 2 to 4 years: 180mg up to four times daily.

• 4 to 6 years: 240mg up to four times daily.

• 6 to 8 years: 250mg up to four times daily. 

• 8 to 10 years: 375mg up to four times daily. 

• 10 to 12 years: 500mg up to four times daily. [3]

For each of the above, do not give more than 4 doses in 24 hours. [1]

What should I do if I miss a dose of acetaminophen?

Acetaminophen is mostly taken when necessary to relieve pain. If you missed a dose, you can take it when you remember. But, if it is almost time for your next dose, skip the dose you missed. Do not take more of the drug because you are trying to make up for the dose you missed. [1]

Warnings on acetaminophen

• Taking an overdose of acetaminophen can damage the liver, and cause death.
• If you have severe liver disease, avoid using acetaminophen.
• Avoid taking more than one medication that contains acetaminophen at a time as it can cause an overdose.
• While hypersensitivity is rare, report immediately to a physician if your skin becomes red, blisters or peels after taking acetaminophen. [1]

What are the adverse effects of acetaminophen?

Some common adverse effects of oral or rectal acetaminophen include: [4]

• Kidney toxicity
• Anaemia
• Skin rash
• Liver toxicity
• Hypersensitivity reactions

Other side effects that accompany intravenous administration of acetaminophen include: [4]

• Nausea
• Vomiting
• Constipation
• Abdominal pain 

What should I avoid when using acetaminophen?

• It is safer to avoid alcohol while on acetaminophen, especially if you have a liver condition.

• Avoid anything that can harm the liver including herbal supplements. [5]

What other drugs interact with acetaminophen?

• Isoniazid (a drug to treat tuberculosis)

• Warfarin (a drug to prevent blood clotting)

• Levonorgestrel (a drug used to prevent pregnancy)

• Tinidazole (an antibiotic)

• Carbamazepine (a drug used for convulsions)

• Acetazolamide (a drug to treat glaucoma) [6]

What if I overdose on acetaminophen?

An overdose of acetaminophen can cause symptoms such as loss of appetite, stomach pain, nausea, vomiting, sweating, weakness and confusion. Other symptoms that occur later may include pain in the upper stomach, dark urine, and yellowing of the skin or the white part of your eyes. Seek urgent medical assistance if you take an overdose of acetaminophen. [1]

Conclusion

In conclusion, you are now better informed with essential facts about acetaminophen; from its use, to dosage guidelines, potential side/adverse effects and drug interactions.

The knowledge you have should help you make use of acetaminophen safely and effectively. Remember to always consult a healthcare professional if you have questions or concerns.

References

1. Drugs.com. Acetaminophen Uses, Dosage & Side Effects. [Internet] Last updated 2023 Aug. 6. Cited August 15, 2024. Available from here.

2. Ohashi, N., & Kohno, T. Analgesic Effect of Acetaminophen: A review of known and Novel mechanisms of action. Frontiers in Pharmacology, 2020; 11. doi: 10.3389/fphar.2020.580289. Available from here.

3. The Pharmaceutical Journal. The Royal Pharmaceutical Society’s Official Journal. Paracetamol use in infants and young children. [Internet] 2023, July 3. Cited August 15, 2024. Available from here.

4  Gerriets V, Anderson J, Patel P, et al. Acetaminophen. [Internet] Updated 2024 Jan 11. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Cited August 15, 2024. Available from here.

5. NHS UK. Common questions about paracetamol for adults. Internet. 2022, October 21. Cited August 15, 2024. Available from here.

6. Medscape. Drug Interactions Checker - Medscape Drug Reference Database. Acetaminophen (OTC) [Internet, n.d.] Cited August 15, 2024. Available from here

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Published: August 19, 2024

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