II. Indications
III. Contraindications
- Severe hepatic insufficiency
- Severe progressive liver disease
- Acetaminophen Hypersensitivity
IV. Mechanism
- Acetaminophen is derived from Acetanilide, and Analgesic discovered in the 1880s
-
Analgesic
- May inhibit the nitric oxide pathway, raising the pain threshold via the Neurotransmitters NMDA and substance P
- Antipyretic
- May modulate Prostaglandin synthesis and release
- May effect Temperature Regulation in the Anterior Hypothalamus
- No significant antiinflammatory effect
- Weak Prostaglandin synthesis inhibitor
V. Medications
- Acetaminophen
- Chewable: 80 mg
- Elixir: 160 per 5 ml
- Dropper: 80 mg per 0.8 ml
- Suppository: 120 mg, 325 mg, 650 mg
- Tablet
- Regular strength: 325 mg
- Extra-Strength: 500 mg
- Acetaminophen Intravenous (Ofirmev)
- Available in generic formulation expected in 2022
- Acetaminophen Combination agents with Opioids
- Vicodin or Lortab (Acetaminophen with Hydrocodone)
- Percocet (Acetaminophen with Oxycodone)
- Acetaminophen Combination agents - miscellaneous
- Excedrin Migraine (Acetaminophen with Aspirin and Caffeine)
- Sudafed PE (Acetaminophen with Diphenhydramine and Phenylephrine)
VI. Dosing: Children
- Avoid overdosage of the Acetaminophen component at all cost (err on the side of underdosage)
- Acetaminophen
- Well hydrated child: 15 mg/kg every 6 hours
- Dehydration risk: 10 mg/kg every 6 hours
- Dosing by age (use only for an isolated single dose)
- Use measured weight based dosing for any subsequent doses!
- Age >2 months (5 kg): 80 mg per dose
- Age >4 months (6.5 kg): 100 mg per dose
- Age >6 months (8 kg): 120 mg per dose
- Age >12 months (10 kg): 160 mg per dose
- Age >2 years (13 kg): 200 mg per dose
- Age >3 years (15 kg): 240 mg per dose
- Age >5 years (19 kg): 280 mg per dose
- Maximum
- Do not exceed 75 mg/kg/day (up to 4 grams per day)
VII. Dosing: Adults (weight >50 kg)
- Regular Dose: 650 mg orally every 4 to 6 hours prn
- Higher Dose (Osteoarthritis)
- Regular Strength Tablet (325 mg)
- Take 975 mg (3 tablets) orally every 6 hours
- Extra-Strength Tablet (500 mg)
- Take 1000 mg (2 tablets) orally every 6 hours
- Regular Strength Tablet (325 mg)
- Maximum: 4 grams per day
- Limit to 2 grams per day maximum in advanced liver disease or severe Alcohol Use Disorder
- Do not exceed 12 regular strength tablets (325 mg)
- Do not exceed 8 extra-strength tablets (500 mg)
VIII. Pharmacokinetics
- Similar potency and time-effect curve to Aspirin
- Duration: 4 hours
- Onset: 10 to 60 min (within 5-10 min for intravenous form)
IX. Adverse Effects: Hepatotoxicity
X. Safety: Pregancy
- FDA Pregnancy Category B
- As with all Medications in Pregnancy, use the lowest effective dose in concert with non-pharmacologic measures
- Acetaminophen continues to be the preferred Analgesic in pregnancy without major safety concerns
- (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)
- However Acetaminophen association with ADHD is without evidence of causality
- Cooper (2014) JAMA Pediatr 168(4):306-307 [PubMed]
- Gou (2019) Aust N Z J Psychiatry 53(3): 195-206 [PubMed]
- Matosich (2024) Am Fam Physician 109(1): 81-2 [PubMed]
- 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
XI. Efficacy: Rheumatologic Conditions
- Scheduled dosing much more effective than prn
- Tylenol 1000 mg four times daily is as effective as Tylenol #3
XII. Precautions
- Dehydration predisposes to overdosage
- Never exceed maximum daily dosage (hepatotoxicity)
XIII. Resources
XIV. References
- LoVecchio (2021) Crit Dec Emerg Med 35(12): 32
- (2000) Med Lett Drugs Ther 42(1085):73-8 [PubMed]
- (1996) Med Lett Drugs Ther 38:5 [PubMed]
- Katzung (1989) Basic and Clinical Pharmacology
Images: Related links to external sites (from Bing)
Related Studies
| acetaminophen (on 12/21/2022 at Medicaid.Gov Survey of pharmacy drug pricing) | ||
| ACETAMINOPHEN 120 MG SUPPOS | Generic OTC | $0.30 each |
| ACETAMINOPHEN 160 MG/5 ML LIQ | Generic OTC | $0.01 per ml |
| ACETAMINOPHEN 160 MG/5 ML SOLN | Generic OTC | $0.02 per ml |
| ACETAMINOPHEN 325 MG GELCAP | Generic OTC | $0.02 each |
| ACETAMINOPHEN 325 MG TABLET | Generic OTC | $0.02 each |
| ACETAMINOPHEN 500 MG CAPLET | Generic OTC | $0.03 each |
| ACETAMINOPHEN 500 MG GELCAP | Generic OTC | $0.03 each |
| ACETAMINOPHEN 500 MG SOFTGEL | Generic OTC | $0.05 each |
| ACETAMINOPHEN 500 MG TABLET | Generic OTC | $0.03 each |
| ACETAMINOPHEN 650 MG SUPPOS | Generic OTC | $0.29 each |
| ACETAMINOPHEN ER 650 MG CAPLET | Generic OTC | $0.07 each |
| ACETAMINOPHEN ER 650 MG TABLET | Generic OTC | $0.07 each |
| ACETAMINOPHEN PM CAPLET | Generic OTC | $0.05 each |
| ACETAMINOPHEN-COD #2 TABLET | Generic | $0.16 each |
| ACETAMINOPHEN-COD #3 TABLET | Generic | $0.13 each |
| ACETAMINOPHEN-COD #4 TABLET | Generic | $0.31 each |
| ACETAMINOPHEN-CODEINE 120 MG-12 MG/5 ML SOLUTION | Generic | $0.02 per ml |
Ontology: Acetaminophen (C0000970)
| Definition (NCI_NCI-GLOSS) | A drug that reduces pain and fever (but not inflammation). It belongs to the family of drugs called analgesics. |
| Definition (NCI) | A p-aminophenol derivative with analgesic and antipyretic activities. Although the exact mechanism through which acetaminophen exert its effects has yet to be fully determined, acetaminophen may inhibit the nitric oxide (NO) pathway mediated by a variety of neurotransmitter receptors including N-methyl-D-aspartate (NMDA) and substance P, resulting in elevation of the pain threshold. The antipyretic activity may result from inhibition of prostaglandin synthesis and release in the central nervous system (CNS) and prostaglandin-mediated effects on the heat-regulating center in the anterior hypothalamus. |
| Definition (MSH) | Analgesic antipyretic derivative of acetanilide. It has weak anti-inflammatory properties and is used as a common analgesic, but may cause liver, blood cell, and kidney damage. |
| Definition (CSP) | analgesic antipyretic derivative of acetanilide; weak antiinflammatory properties and is used as a common analgesic, but may cause liver, blood cell, and kidney damage. |
| Concepts | Pharmacologic Substance (T121) , Organic Chemical (T109) |
| MSH | D000082 |
| SnomedCT | 384977007, 264317002, 387517004, 90332006 |
| LNC | LP14712-1, MTHU003399 |
| English | Acetamidophenol, Acetaminophen, Acetominophen, Hydroxyacetanilide, p-Acetamidophenol, p-Hydroxyacetanilide, Paracetamol, N-Acetyl-p-aminophenol, Acetamide, N-(4-hydroxyphenyl)-, N-(4-Hydroxyphenyl)acetanilide, PARACETAMOL, 4-Hydroxyacetanilide, N-(4-Hydroxyphenyl)acetamide, acetaminophen, ACETAMINOPHEN, 4-hydroxyacetanilide, acetaminophen (medication), analgesics acetaminophen, APAP, Paracetamol - chemical, Acetaminophen [Chemical/Ingredient], paracetamol, Paracetamol (substance), Paracetamol - chemical (substance), Paracetamol product, Acetaminophen (product), Acetaminophen (substance), Acetaminophen product, ACMP |
| Swedish | Acetaminofen |
| Czech | acetaminofen, paracetamol |
| Finnish | Parasetamoli |
| Italian | Idrossiacetanilide, Acetaminofenolo, Paracetamolo, N-acetile-p-amminofenolo, N-(4-idrossifenil)acetanilide, p-Acetaminofenolo, p-Idrossiacetanilide, Acetominofene, Acetaminofene |
| Russian | ATSETAMIDOFENOL, ATSETAMINOFEN, PARATSETAMOL, GIDROKSIATSETANILID, АЦЕТАМИДОФЕНОЛ, АЦЕТАМИНОФЕН, ГИДРОКСИАЦЕТАНИЛИД, ПАРАЦЕТАМОЛ |
| Japanese | ピリナジン, ピレチノール, N-アセチルアミノフェノール, ヒドロキシアセトアニリド, アニルーメ, アセトアミドフェノール, オキシアセトアニリド, アフロギス, カロナール, アルピニー, パラセタモール, アセトアミノフェノール, アンヒバ, コカール, リングルサット, アスペイン, タイレノール, アセフェン, サールツー, アセトアミノフェン, カルポール, ドリプラン, キオフィーバ |
| Spanish | paracetamol, acetaminofeno (producto), paracetamol (producto), Acetaminofén, paracetamol (sustancia), Acetaminofeno, acetaminofeno (sustancia), acetaminofeno, Paracetamol, Acetamidofenol, Hidroxiacetanilida |
| Croatian | ACETAMINOFEN |
| French | 4-Hydroxyacétanilide, Paracétamol, Acétaminophène, p-Hydroxyacétanilide |
| Polish | Paracetamol, Acetaminofen |
| Norwegian | Acetaminophen, Paracetamol |
| German | Acetamidophenol, Acetaminophen, Azetaminophen, Hydroxyacetanilid, Paracetamol |
| Portuguese | Paracetamol, Acetamidofenol, Acetaminofen, Hidroxiacetanilida |
Ontology: Tylenol (C0699142)
| Concepts | Pharmacologic Substance (T121) , Organic Chemical (T109) |
| MSH | D000082 |
| Italian | Tylenol |
| English | tylenol, Tylenol |
| Czech | Tylenol |
