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Acetaminophen

Classification

Analgesic

Antipyretic

Indications

FR: Mild to moderate pain (PO only)

PCP: Mild to moderate pain and pyrexia (PO/IV)

Contraindications

Hypersensitivity to acetaminophen or any component of the formulation
Severe hepatic impairment or severe active liver disease
Do not administer if acetaminophen has been given within the past 4 hours (from all sources), or if total acetaminophen intake within the last 24 hours exceeds the daily maximums (refer below for maximums).
Do not administer acetaminophen if overdose is suspected, indicated by symptoms such as nausea, vomiting, or right upper quadrant pain

Caution:

Hepatic impairment, heavy alcohol use, chronic malnutrition, and hypovolemia

Adult dosages

See → CPG E08: Pain Management for additional guidance

Oral administration

FR: Analgesia

PCP: Analgesia and antipyresis

500 - 1,000 mg PO
May repeat once after 4 hours
24 hour maximum dose, from all sources and all routes of administration: 4,000 mg
In patients with suspected or known liver dysfunction (e.g., advanced chronic liver disease, cirrhosis, heavy alcohol use) or malnutrition, the 24-hour maximum should be lowered to 2,000 mg.
May be used concurrently with ibuprofen for analgesia

Intravenous administration

Intravenous and oral doses are equivalent on a mg-to-mg basis.

PCP: Analgesia and antipyresis

≥50 kg: 1000 mg IV q6h as required (see above for daily maximums)
- Infuse 1000 mg/100 mL bag undiluted over 15 minutes using a standard 10 gtts/mL IV set (66 gtts/min)
Not authorized for use in patients <50 kg.

ACP: Analgesia and antipyresis

≥50 kg: 1000 mg IV q6h as required (see above for daily maximums)
- Infuse 1000 mg/100 mL bag undiluted over 15 minutes using a standard 10 gtts/mL IV set (66 gtts/min)
<50 kg: 15 mg/kg IV q6h as required (see above for daily maximums).
- Withdraw appropriate volume from premixed bag of 1,000 mg/100 mL and transfer to the supplied empty IV bag. The new bag must be labeled and infused undiluted over 15 minutes. Discard any unused portion of the original bag.

Do not add other medications to the acetaminophen bag.

Pediatric Considerations And Dosing

Oral administration

EMR: Analgesia

<30 kg: 15 mg/kg PO (use liquid preparation)
30-50 kg: 500 mg PO (may use liquid preparation or tablets, depending on patient ability)
>50 kg: 500- 1,000 mg PO
May repeat once after 4 hours
24 hour maximum cumulative dose: 75 mg/kg or 4,000 mG
Do not exceed 5 doses in 24-hours in patients less than 12 years of age

Intravenous administration

PCP: Analgesia and antipyresis

In children over 12 years and >50 kg: 1,000 mg
- Maximum single dose: 1,000 mg
- 24 hour maximum cumulative dose: 75 mg/kg/day
- Not authorized for use in patients less than 12 years OR <50 kg.

ACP: Analgesia and antipyresis

In children 2-12 years and <50 kg: 15 mg/kg IV q6h as required
- For doses less than 1000 mg the appropriate dose of the drug must be withdrawn from the supplied acetaminophen bag and added to an empty IV bag. The new bag must be labeled and infused undiluted over 15 minutes using a drip set. Discard any unused portion of the original bag.
- See chart below for example weights and dosages
Maximum single dose: 750 mg
24 hour maximum cumulative dose: 75 mg/kg/day

Table 1. Intravenous acetaminophen infusion dosing (15 mg/kg infused over 15 minutes)

Age	Initial Dose	Repeat Dose	Dose Interval	Concentration	Volume	Max Dose
12–Adult	1000mg	1000mg	4-6 hours	10 milligrams in 1mL	100 ml	4gr/24hr
11 Years	500mg	500mg	4-6 hours	10 milligrams in 1mL	50 ml	2gr/24hr
10 Years	500mg	500mg	4-6 hours	10 milligrams in 1mL	50 ml	2gr/24hr
9 Years	500mg	500mg	4-6 hours	10 milligrams in 1mL	50 ml	2gr/24hr
8 Years	300mg	300mg	4-6 hours	10 milligrams in 1mL	30 ml	1.2gr/24hr
7 Years	300mg	300mg	4-6 hours	10 milligrams in 1mL	30 ml	1.2gr/24hr
6 Years	300mg	300mg	4-6 hours	10 milligrams in 1mL	30 ml	1.2gr/24hr
5 Years	250mg	250mg	4-6 hours	10 milligrams in 1mL	25 ml	1gr/24hr
4 Years	250mg	250mg	4-6 hours	10 milligrams in 1mL	25 ml	1gr/24hr
3 Years	250mg	250mg	4-6 hours	10 milligrams in 1mL	25 ml	1gr/24hr
2 Years	150mg	150mg	4-6 hours	10 milligrams in 1mL	15 ml	600mg/24hr
18 Months	150mg	150mg	4-6 hours	10 milligrams in 1mL	15ml	600mg/24hr
12 Months	150mg	150mg	4-6 hours	10 milligrams in 1mL	15 ml	600mg/24hr
9 Months	50mg	50mg	4-6 hours	10 milligrams in 1mL	5 ml	200mg/24hr
6 Months	50mg	50mg	4-6 hours	10 milligrams in 1mL	5 ml	200mg/24hr
3 Months	N/A	N/A	N/A	N/A	N/A	N/A
1 Month	N/A	N/A	N/A	N/A	N/A	N/A
Birth	N/A	N/A	N/A	N/A	N/A	N/A

N/A: not authorized for use

Caution:Verify dosing in milligrams (mg) with volume in milliliters (mL) to ensure accuracy. There is a potential for a ten-fold dosing error.

Do not add other medications to the acetaminophen bag.

Mechanism Of Action

Acetaminophen inhibits prostaglandin synthetase in the central nervous system, reducing pain and pyrexia.

Pharmacokinetics

Oral:

Onset: 30 minutes
Peak: 1-3 hours
Duration: 4 hours

Intravenous:

Onset: 15 minutes (matching rate of administration)
Peak: 1 hour
Duration: 4-6 hours (analgesia) and > 6 hours (antipyresis)

Adverse Effects

Adverse reactions are uncommon with short-term use of acetaminophen. Nausea and vomiting can occur with IV formulation.
Hypotension has been reported with IV infusion, particularly in critically ill patients. Monitor baseline BP and then q15min x 3.
Rash and hives are rarely reported, but can occur.

Overdose

Toxicity may occur after a single dose of more than 7.5 g (adults) or 150 mg/kg (pediatrics). Clinical findings of toxicity include nausea, vomiting, and/or right upper quadrant pain.

Warning And Precautions

Acetaminophen is the leading cause of serious liver injury in Canada. Patients with pre-existing liver disease (regardless of underlying cause), chronic users of acetaminophen, and pediatrics are at most risk. Acetaminophen is a component of many over-the-counter medications and patients may inadvertently be consuming much higher doses than expected. Paramedics must ensure that a complete medication history is obtained prior to the administration of acetaminophen, including over-the-counter preparations.

Drug Interactions

Alcohol may potentiate acetaminophen’s hepatoxic effects. Chronic acetaminophen use can impact INR levels, potentially affecting patients taking warfarin.

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Acetaminophen

Classification

Indications

Contraindications

Adult dosages

Oral administration

Intravenous administration

Pediatric Considerations And Dosing

Oral administration

Intravenous administration

Mechanism Of Action

Pharmacokinetics

Adverse Effects

Overdose

Warning And Precautions

Drug Interactions