Acetaminophen

Fever
Mild to Moderate Pain
1. Combined with other Analgesics for moderate to severe pain

Acetaminophen is derived from Acetanilide, and Analgesic discovered in the 1880s
Analgesic
1. May inhibit the nitric oxide pathway, raising the pain threshold via the Neurotransmitters NMDA and substance P
Antipyretic
1. May modulate Prostaglandin synthesis and release
2. May effect Temperature Regulation in the Anterior Hypothalamus
No significant antiinflammatory effect
1. Weak Prostaglandin synthesis inhibitor

Acetaminophen
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. Acetaminophen Intravenous (Ofirmev)
  1. Available in generic formulation expected in 2022
Acetaminophen Combination agents with Opioids
1. Vicodin or Lortab (Acetaminophen with Hydrocodone)
2. Percocet (Acetaminophen with Oxycodone)
Acetaminophen Combination agents - miscellaneous
1. Excedrin Migraine (Acetaminophen with Aspirin and Caffeine)
2. Sudafed PE (Acetaminophen with Diphenhydramine and Phenylephrine)

Avoid overdosage of the Acetaminophen component at all cost (err on the side of underdosage)
Acetaminophen
1. Well hydrated child: 15 mg/kg every 6 hours
2. Dehydration risk: 10 mg/kg every 6 hours
3. Dosing by age (use only for an isolated single dose)
  1. Use measured weight based dosing for any subsequent doses!
  2. Age >2 months (5 kg): 80 mg per dose
  3. Age >4 months (6.5 kg): 100 mg per dose
  4. Age >6 months (8 kg): 120 mg per dose
  5. Age >12 months (10 kg): 160 mg per dose
  6. Age >2 years (13 kg): 200 mg per dose
  7. Age >3 years (15 kg): 240 mg per dose
  8. 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)

Regular Dose: 650 mg orally every 4 to 6 hours prn
Higher Dose (Osteoarthritis)
1. Regular Strength Tablet (325 mg)
  1. Take 975 mg (3 tablets) orally every 6 hours
2. Extra-Strength Tablet (500 mg)
  1. Take 1000 mg (2 tablets) orally every 6 hours
Maximum: 4 grams per day
1. Limit to 2 grams per day maximum in advanced liver disease or severe Alcohol Use Disorder
2. Do not exceed 12 regular strength tablets (325 mg)
3. Do not exceed 8 extra-strength tablets (500 mg)

FDA Pregnancy Category B
As with all Medications in Pregnancy, use the lowest effective dose in concert with non-pharmacologic measures
1. Acetaminophen continues to be the preferred Analgesic in pregnancy without major safety concerns
2. (2021) Presc Lett 28(11): 63-4
May be associated with increased risk of ADHD in children with prolonged regular use (>4 to 6 weeks, esp. third trimester)
1. However Acetaminophen association with ADHD is without evidence of causality
2. Cooper (2014) JAMA Pediatr 168(4):306-307 [PubMed]
3. Gou (2019) Aust N Z J Psychiatry 53(3): 195-206 [PubMed]
4. Matosich (2024) Am Fam Physician 109(1): 81-2 [PubMed]
5. Sznajder (2022) PLoS One 17(9): e0272593 [PubMed]
Untreated fever over 101 F (esp. first trimester) is also associated with increased fetal risks in pregnancy
1. Dreier (2014) Pediatrics 133(3): e674-88 [PubMed]