Acetaminophen

Aka: Acetaminophen, Tylenol, Paracetamol, N-acetyl-p-aminophenol

1. Indications
   1. Pain
   2. Fever (>102 F or Fever at bedtime)
2. Efficacy: Rheumatologic Conditions
   1. Scheduled dosing much more effective than prn
   2. Tylenol 1000 mg qid is as effective as Tylenol #3
3. Dosing: Children
   1. Avoid overdosage of the Acetaminophen component at all cost (err on the side of underdosage)
   2. Acetaminophen
      1. Well hydrated child: 15 mg/kg every 4 to 6 hours
      2. Dehydration risk: 10 mg/kg every 4 to 6 hours
      3. Dosing by age
         1. Age >2 months (5 kg): 80 mg per dose
         2. Age >4 months (6.5 kg): 100 mg per dose
         3. Age >6 months (8 kg): 120 mg per dose
         4. Age >12 months (10 kg): 160 mg per dose
         5. Age >2 years (13 kg): 200 mg per dose
         6. Age >3 years (15 kg): 240 mg per dose
         7. Age >5 years (19 kg): 280 mg per dose
      4. Maximum
         1. Do not exceed 75 mg/kg/day (up to 4 grams per day)
4. Dosing: Adults
   1. Regular Dose: 650 mg orally every 4 to 6 hours prn
   2. Higher Dose (Osteoarthritis)
      1. Regular Strength Tablet (325 mg)
         1. Take 975 mg (3 tablets) PO every 6 hours
      2. Extra-Strength Tablet (500 mg)
         1. Take 1000 mg (2 tablets) PO every 6 hours
   3. Maximum: 4 grams per day
      1. Do not exceed 12 regular strength tablets (325 mg)
      2. Do not exceed 8 extra-strength tablets (500 mg)
5. Pharmacokinetics
   1. Similar potency and time-effect curve to Aspirin
   2. Duration: 4 hours
6. Preparations
   1. Chewable: 80 mg
   2. Elixir: 160 per 5 ml
   3. Dropper: 80 mg per 0.8 ml
   4. Suppository: 120 mg, 325 mg, 650 mg
   5. Tablet
      1. Regular strength: 325 mg
      2. Extra-Strength: 500 mg
   6. Combination agents with Opioids
      1. Vicodin or Lortab (Acetaminophen with Hydrocodone)
      2. Percocet (Acetaminophen with Oxycodone)
   7. Combination agents - miscellaneous
      1. Excedrin Migraine (Acetaminophen with Aspirin and Caffeine)
      2. Sudafed PE (Acetaminophen with Diphenhydramine and Phenylephrine)
7. Adverse Effects: Hepatotoxicity
   1. See Acetaminophen Toxicity
   2. Drug-Induced Skin Reaction (Stevens Johnson Syndrome, Toxic Epidermal Necrolysis)
      1. http://www.fda.gov/downloads/Drugs/DrugSafety/UCM363052.pdf
8. Safety: Pregancy
   1. FDA Pregnancy Category B
   2. May be associated with increased risk of ADHD in children with prolonged regular use (>6 weeks)
      1. However Acetaminophen association with ADHD is very weak, and without any evidence of causality (observational study)
      2. Cooper (2014) JAMA Pediatr 168(4):306-307 [PubMed]
   3. Untreated fever over 101 F is also associated with increased fetal risks in pregnancy (and NSAIDs present additional risks)
      1. Dreier (2014) Pediatrics 133(3): e674-88 [PubMed]
9. Precautions
   1. Dehydration predisposes to overdosage
   2. Never exceed maximum daily dosage (hepatotoxicity)
10. References
    1. (2000) Med Lett Drugs Ther 42(1085):73-8 [PubMed]
    2. (1996) Med Lett Drugs Ther 38:5 [PubMed]
    3. Katzung (1989) Basic and Clinical Pharmacology