 Tylenol (acetaminophen) |
 Panadol (paracetamol) |
Acetaminophen (USA & Japan) (a-seet-a-min-oh-fen) or paracetamol (rest of the world) is a non-opioid analgesic and antipyretic agent that is commonly used as a first line approach to treat fever and mild pain. It is on the World Health Organization’s List of Essential Medicines and in most countries is available both over-the-counter and on prescription. Acetaminophen/paracetamol has a good safety profile and was first first marketed as Tylenol in 1955 by McNeil Laboratories for pain and fever reliever in children.
Mechanism of action:
Not totally clear.
Analgesic: Probably activates the descending serotonergic inhibitory pathways in the CNS.
Antipyretic: Inhibits the hypothalamic heat-regulating center.
No anti-inflammatory effects.
Pharmacokinetics:
Rapidly absorbed from GI tract
Protein binding: 10%–40%.
Distributed to most body tissues.
Metabolized predominantly in liver.
Excreted in urine.
Half-life: 1–4 hrs
Onset: 30 minutes if oral; 8 minutes if intravenous
Adverse effects:
Common: skin rash; nausea; abdominal pain, liver damage (jaundice)
Rare: Hypersensitivity reaction; Stevens–Johnson syndrome.
The FDA (USA) requires all prescription drugs containing acetaminophen to carry a black box warning that an overdose can result in liver transplant or death.
Acetaminophen Toxicity:
Early signs: Anorexia, nausea, excessive sweating, fatigue.
Later signs: vomiting, stomach tenderness, elevated liver enzymes
Treatment: Acetylcysteine
Contraindications:
History of hypersensitivity to acetaminophen; active liver disease.
Precautions:
Renal or liver impairment; chronic malnutrition
Pregnancy/Lactation: can crosse placenta and distributed in breast milk.
Has been routinely used in all stages of pregnancy and appears safe for use in short term.
Dosage:
Maximum recommended daily oral dosage in adults is 500 to 1000 mg every 4 to 6 hours
Interactions:
Hepatotoxic medications (eg phenytoin), strong CYP3A4 inducers (eg carbamazepine) may increase the risk of hepatotoxicity.
Probenecid may increase concentration.
Brand names: Tylenol (acetaminophen); Panadol (paracetamol); Calpol; Panamax; Acephen; FeverAll; Ofirmev; and many others.
Chemical formula: C8H9NO2
Systematic chemical name: N-acetyl-para-aminophenol
Availability: Over-the-counter; prescription; suppository; injectable. Can be combined with codeine.
Patient Education:
Follow the directions on the label and take the recommended dose.
Do not take more than one medicine that contains acetaminophen/paracetamol (increases risk of overdose/toxicity).
Keep out of reach of children.
Does not need to be taken with food.
Drinking a small amount of alcohol while taking it is usually safe (more risky if have liver disease).
Box Label for Tylenol:
Box label for Tylenol
In Australia, Paracetamol is on the National Podiatry Scheduled Medicines List for use by authorised podiatrists, even though it is an over-the-counter medication.
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