Paracetamol (Acetaminophen): Uses, Dosage, Side Effects, and More
1. Drug Name
Generic Name: Paracetamol
Brand Name(s):
- Pakistan: Calpol, Pacimol
- India: Crocin, Dolo
- United States: Tylenol, Panadol
- United Kingdom: Paracetamol, Panadol
2. Pharmacological Class
Class: Analgesic and Antipyretic
Subclass: Para-aminophenol derivatives
3. Mechanism of Action
Paracetamol acts centrally in the brain, inhibiting the synthesis of prostaglandins, which are mediators of pain and fever. Unlike NSAIDs, it has little anti-inflammatory activity.
4. Indications
Primary Indications: Treatment of mild to moderate pain (headache, toothache, muscle pain, back pain) and reduction of fever.
Off-label Uses: Management of osteoarthritis, menstrual pain, and as an adjunct for severe pain.
5. Dosage and Administration
Standard Dosage:
- Adults: 325-650 mg every 4-6 hours, not to exceed 4000 mg per day.
- Children: 10-15 mg/kg every 4-6 hours, not to exceed 5 doses in 24 hours.
Route of Administration: Oral (tablets, capsules, liquid), rectal (suppositories).
Special Populations:
- Pediatric: Dosing is weight-based and age-based.
- Geriatric: Use lower doses to avoid toxicity, particularly in those with decreased renal function.
6. Pharmacokinetics
Absorption: Rapidly and almost completely absorbed from the gastrointestinal tract.
Distribution: Widely distributed in body tissues, crosses the placenta, and small amounts are excreted in breast milk.
Metabolism: Primarily metabolized in the liver via conjugation with glucuronic acid.
Excretion: Excreted primarily by the kidneys, with 90% excreted within 24 hours of ingestion.
Half-life: 1-4 hours in healthy adults.
7. Contraindications
Paracetamol is contraindicated in patients with known hypersensitivity to paracetamol. Use caution in patients with severe hepatic impairment.
8. Warnings and Precautions
Exceeding the recommended dosage can lead to severe liver damage. Avoid consuming alcohol while taking paracetamol, as it can increase the risk of liver toxicity.
9. Side Effects
Common Side Effects: Nausea, vomiting, and abdominal pain.
Serious Side Effects: Liver toxicity (in overdose situations), which may lead to liver failure.
10. Drug Interactions
Major Interactions: Warfarin (increased risk of bleeding due to inhibition of hepatic metabolism), alcohol (increased risk of hepatotoxicity), and certain antiepileptic drugs (phenytoin, carbamazepine) which may lead to hepatotoxicity.
Minor Interactions: Metoclopramide (increases gastric emptying), and cholestyramine (reduces paracetamol absorption).
11. Pregnancy and Lactation
Pregnancy Category: Generally considered safe when used at recommended doses during pregnancy.
Breastfeeding Considerations: Small amounts of paracetamol are excreted in breast milk, but not likely to be harmful to the infant when used at recommended doses.
12. Patient Counseling Information
Key Points for Patients:
- Take paracetamol exactly as directed on the label or as prescribed by your doctor.
- Avoid taking more than the recommended dose.
- Seek medical help immediately if you have symptoms of liver damage, even if you have taken paracetamol before and had no reaction.
Administration Tips:
- Do not crush or chew extended-release tablets. Swallow them whole.
- Use a suitable measuring device (not a household spoon) for liquid formulations.