What is the recommended dosage of paracetamol (acetaminophen) for a patient with considerations for age, weight, medical history, and potential drug interactions?

Paracetamol (Acetaminophen) Dosing Recommendations

For healthy adults, the standard dose is 650-1000 mg every 4-6 hours with a maximum of 4000 mg per 24 hours, but for chronic daily use or patients with any risk factors, limit to 3000 mg per day to minimize hepatotoxicity risk. 1, 2, 3

Standard Adult Dosing

• Single dose: 650-1000 mg every 4-6 hours 2, 4
• Maximum daily dose: 4000 mg per 24 hours (FDA-approved maximum) 1, 5
• Minimum interval between doses: 4 hours 2
• Maximum number of doses: 6 doses in 24 hours 2, 5

Critical Safety Warning for All Patients

When prescribing paracetamol at any dose, explicitly counsel patients to avoid ALL other paracetamol-containing products including over-the-counter cold remedies, sleep aids, and opioid combination products. 6, 1, 3 This is the most common cause of unintentional overdose. 3

Conservative Dosing for Chronic Use (>14 Days)

For any patient requiring daily paracetamol beyond 2 weeks, reduce maximum daily dose to 3000 mg per day. 1, 2, 3 This recommendation comes from multiple sources:

• The National Comprehensive Cancer Network specifically recommends limiting chronic administration to 3000 mg daily to minimize hepatotoxicity risk 1, 2
• Repeated supratherapeutic ingestions (doses just above therapeutic range) carry worse prognosis than acute single overdoses, accounting for approximately 30% of paracetamol overdose admissions 1, 2, 3
• Studies demonstrate that even therapeutic doses of 4000 mg/day for 14 days can cause ALT elevations >3× normal in 31-41% of healthy adults 1

High-Risk Populations Requiring Dose Reduction

Liver Disease

Maximum 2000-3000 mg per day for patients with cirrhosis or chronic liver disease. 1, 2, 3 Severe liver damage may occur if an adult takes more than 6 doses in 24 hours or exceeds 4000 mg. 5

Chronic Alcohol Users

Limit to 2000-3000 mg per day maximum. 2, 3 Hepatotoxicity can occur at doses ≤4000 mg in chronic alcohol users, with case series demonstrating severe hepatotoxicity and mortality at doses as low as 5-8.75 g/day. 1 The FDA label explicitly warns against taking paracetamol with 3 or more alcoholic drinks every day. 5

Elderly Patients (≥60 Years)

Reduce maximum daily dose to 3000 mg per day, though single dose remains 1000 mg. 1, 2 For frail elderly, start at the lower end of dosing range (325 mg per dose). 2

Pediatric Dosing (≥12 Years)

650 mg every 4-6 hours, maximum 6 doses in 24 hours, not exceeding 4000 mg total daily. 2 For younger children, use 10-15 mg/kg every 4-6 hours with maximum 60 mg/kg/day. 2

Prescription Combination Products

The FDA mandates that prescription combination products contain ≤325 mg paracetamol per dosage unit. 1, 2, 3 This reduces risk when patients take multiple doses throughout the day.

Critical Care/ICU Dosing

For critically ill adults, use 1000 mg every 6 hours (IV, oral, or rectal) as adjunct to opioids. 1, 2 Important caveat: IV paracetamol may cause hypotension in up to 50% of patients, which may preclude use in hemodynamically unstable patients. 1, 2

Pain Management Algorithm When Paracetamol Alone Is Insufficient

Do NOT exceed 3000 mg daily for chronic use even if pain control is inadequate. 3 Instead:

1. Add topical NSAIDs (preferred in patients ≥75 years) 6
2. Consider intra-articular corticosteroid injections 6
3. Add tramadol if needed 6
4. Consider multimodal approach with topical lidocaine patches or regional nerve blocks 2

Common Pitfalls to Avoid

• Failing to recognize paracetamol in combination products (cold medicines, sleep aids, pain relievers) leading to unintentional overdose 1, 3
• Using multiple paracetamol-containing products simultaneously without tracking total daily intake 3
• Not adjusting dosage for patients with liver disease, chronic alcohol use, or elderly status 3
• Exceeding recommended dosing frequency by taking doses too close together 3

Hepatotoxicity Risk Thresholds

• AST >1000 IU/L indicates developing toxicity 1, 3
• Most acute liver failure occurs with ingestions exceeding 10 grams per day, though severe injury can rarely occur at 3-4 grams per day in patients with risk factors 3
• Serum aminotransferase levels >3500 IU/L are highly correlated with paracetamol toxicity 3

Drug Interactions

Ask patients specifically about warfarin use before prescribing paracetamol. 5 Paracetamol has low risk of drug interactions due to minimal plasma protein binding and hepatic metabolism through glucuronide/sulfate conjugation. 4

Special Circumstances

Paracetamol can be used during pregnancy and lactation and is the non-opioid analgesic of choice in elderly persons or patients with chronic renal insufficiency. 4, 7 It is usually not necessary to reduce dosage in renal insufficiency, even though clearance is reduced. 4