What is the recommended dosage of paracetamol (acetaminophen) for pain and fever relief?

Paracetamol (Acetaminophen) Dosing for Pain and Fever Relief

Standard Adult Dosing

For adults with pain or fever, the recommended single dose is 1000 mg (1 gram) every 4-6 hours, with a maximum daily dose of 4000 mg (4 grams) in 24 hours. 1, 2

• The optimal unit dose for analgesic efficacy in adults is 1 g 3
• Doses can be administered every 4-6 hours as needed, with a maximum of 6 doses in 24 hours 2
• The analgesic effect typically lasts approximately 4-6 hours 4, 3

Dosing by Pain Severity

Mild Pain (Numerical Rating Scale 1-4)

• Paracetamol 500-1000 mg every 4-6 hours is appropriate as first-line therapy 4
• Maximum daily dose remains 4000 mg 4

Moderate Pain (Numerical Rating Scale 5-7)

• Paracetamol 1000 mg can be used alone or combined with other analgesics 4
• When combined with opioids or NSAIDs, paracetamol enhances analgesic effect and may allow lower doses of the other agent 4, 3

Critical Care and Postoperative Settings

• Intravenous paracetamol 1 g every 6 hours is recommended as an adjunct to opioids in critically ill adults to decrease pain intensity and reduce opioid consumption 4
• This dosing significantly reduces opioid requirements by approximately 4.5 mg morphine equivalents over 24 hours 4
• Be aware that IV paracetamol can cause hypotension (mean arterial pressure decrease >15 mmHg in up to 50% of patients) 4

Dose Modifications for Special Populations

Chronic Use

• For prolonged use, limit to 3000 mg daily to reduce hepatotoxicity risk 5
• This lower threshold is particularly important for cancer pain management requiring extended therapy 5

Liver Disease

• Patients with chronic liver disease or cirrhosis should use 2-3 g daily maximum due to altered metabolism and prolonged half-life 5
• Paracetamol is contraindicated in hepatic insufficiency 3
• However, it remains safe at recommended doses in stable cirrhotic patients 6

Elderly Patients

• The standard single dose of 1000 mg and maximum daily dose of 4000 mg generally remain appropriate 6
• No evidence supports routine dose reduction based solely on age 6
• Some guidelines suggest considering a maximum of 3000 mg daily in patients ≥60 years, though this is not universally required 1

Renal Insufficiency

• Paracetamol is the non-opioid analgesic of choice in chronic renal insufficiency 3
• Dose reduction is usually not necessary despite reduced clearance 3

Pediatric Dosing

• 15 mg/kg per dose every 4-6 hours (oral route) 3, 7
• Maximum daily dose: 60 mg/kg/day 3
• This 15 mg/kg dose is significantly more effective than older subtherapeutic doses of ≤10 mg/kg 7
• Paracetamol 15 mg/kg is as effective as NSAIDs (ibuprofen, ketoprofen) but with lower risk of adverse events with repetitive dosing 7

Critical Safety Warnings

Hepatotoxicity Risk

• Severe liver damage may occur if more than 4000 mg is taken in 24 hours 2
• Repeated supratherapeutic ingestions (>4 g/24 hours) can lead to hepatotoxicity, hepatic failure, and death 5
• Risk is increased when combined with 3 or more alcoholic drinks daily 2

Combination Product Pitfall

• Never use paracetamol with any other drug containing acetaminophen 2
• Many prescription and over-the-counter products contain acetaminophen (e.g., opioid combinations, cold/flu medications) 5, 2
• Patients frequently exceed maximum doses inadvertently through combination products 5
• The FDA has limited acetaminophen content in prescription combinations to 325 mg per unit to reduce this risk 1

Overdose Management

• In case of overdose, seek immediate medical attention even without symptoms 2
• Contact Poison Control (1-800-222-1222) immediately 2
• N-acetylcysteine is the antidote and should be administered promptly 4

Formulation Considerations

• Effervescent tablets provide more rapid absorption and faster onset of action compared to conventional tablets 3
• Oral route is preferred when feasible; rectal absorption is slow and irregular 3
• Intravenous formulation is available for patients unable to take oral medications 4

Duration of Use Limits

• Do not use for more than 10 days for pain unless directed by a physician 2
• Do not use for more than 3 days for fever unless directed by a physician 2
• Stop use and consult a physician if symptoms do not improve, new symptoms occur, or pain/fever persists or worsens 2

Efficacy Data

• Approximately 50% of patients achieve at least 50% pain relief over 4-6 hours with paracetamol 1000 mg, compared to 20% with placebo 8
• Number-needed-to-treat for 1000 mg dose is 3.6 (meaning 4 patients need treatment for one to achieve significant benefit over placebo) 8
• About 50% of patients require rescue medication within 4-6 hours, compared to 70% with placebo 8