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Other Names

  • Tylenol
  • Paracetamol


  • Type: Analgesic, Antipyretic
  • Dosage Forms: IV; PO; PR

Adult Dosing

  • PO
    • Regular strength: 650mg q4-6 hours
    • Extra strength: 1000mg q6 hours
    • Extended-release: 1300mg q8 hours
  • Rectal: 650mg q4-6 hours
  • IV:
    • <50 kg: 15mg/kg q6 hours or 12.5mg/kg q4 hours
    • ≥50 kg: 650mg q4 hours or 1000mg q6 hours
  • Maximum daily dose: 4g

Pediatric Dosing

  • 15mg/kg/dose q6 hours

Special Populations

  • Pregnancy Rating: B
  • Lactation Risk Categories: safe
  • Renal Dosing
    • Adult: CrCl 10-50: give q6h, CrCl <10: give q8h
    • Pediatric: CrCl 10-50: give q6h, CrCl <10: give q8h
  • Hepatic Dosing
    • Adult: not defined
    • Pediatric: not defined



  • General
    • When combined with 400 mg ibuprofen, 1000 mg ibuprofen was noninferior to opiates for acute extremity pain in the ED[1]
  • Postoperative pain
    • Cochrane review: single dose of paracetamol provides effective analgesia for about half of patients with acute postoperative pain, for a period of about four hours[2]
  • Osteoarthritis
    • Cochrane review: NSAIDS are superior to Acetaminophen for improving knee and hip pain in people with OA[3]
    • Treatment size is modest, median trial duration only six weeks

Lower Extremity

  • Hip Osteoarthritis
    • Systematic review (2015): no or little efficacy with dubious clinical relevance for treatment of chronic pain due to hip OA[4]
  • Knee Osteoarthritis
    • Systematic review (2015): no or little efficacy with dubious clinical relevance for treatment of chronic pain due to knee OA[4]


  • Allergies
  • Chronic Liver Disease

Adverse Reactions

  • Major
    • Acetaminophen Toxicity
    • Anemia
    • Thrombocytopenia
  • Minor
    • Nausea
    • Rash
    • Headache


  • Half-life: 2-4 hour
  • Metabolism: Liver
  • Excretion: urine
  • Mechanism of Action
    • Poorly understood
    • Antipyretic effect via direct action on the hypothalamic heat-regulating center

Drug Interactions

  • Substances that induce the enzyme CYP2E1 may alter acetaminophen metabolism and increase the risk of hepatotoxicity
  • Chronic oral acetaminophen use at a dose of 4,000 mg/day may increase the INR in patients stabilized on warfarin

Other Considerations

  • When calculating maximum daily dose consider all sources of acetaminophen

See Also


  1. Chang AK, Bijur PE, Esses D, Barnaby DP, Baer J. Effect of a Single Dose of Oral Opioid and Nonopioid Analgesics on Acute Extremity Pain in the Emergency Department: A Randomized Clinical Trial. JAMA. 2017;318(17):1661‐1667.
  2. Toms, Laurence, et al. "Single dose oral paracetamol (acetaminophen) for postoperative pain in adults." Cochrane database of systematic reviews 4 (2008).
  3. Towheed, Tanveer, et al. "Acetaminophen for osteoarthritis." Cochrane Database of Systematic Reviews 1 (2006).
  4. 4.0 4.1 Ennis, Zandra Nymand, et al. "Acetaminophen for chronic pain: a systematic review on efficacy." Basic & clinical pharmacology & toxicology 118.3 (2016): 184-189.
Created by:
John Kiel on 19 May 2020 18:31:25
Last edited:
3 April 2021 02:19:49