OFIRMEV

Clinical safety rating: caution

Comprehensive clinical and safety monograph for OFIRMEV (OFIRMEV).

How it works

OFIRMEV (acetaminophen) is a para-aminophenol derivative with analgesic and antipyretic activity. Its mechanism of action is not fully understood, but it is thought to involve inhibition of cyclooxygenase (COX) enzymes in the central nervous system, with minimal peripheral COX inhibition. It may also act on serotonergic pathways and cannabinoid receptors.

What the body does with it

Metabolism	Acetaminophen is primarily metabolized in the liver via conjugation with glucuronide (50-60%) and sulfate (20-30%). A minor amount is oxidized by cytochrome P450 (CYP2E1, CYP1A2, CYP3A4) to a toxic reactive metabolite (NAPQI), which is normally detoxified by glutathione. At toxic doses, glutathione is depleted, leading to NAPQI accumulation and hepatotoxicity.
Excretion	Primarily renal (85% as sulfate and glucuronide conjugates, 10% as unchanged drug). Less than 5% fecal/biliary.
Half-life	Terminal elimination half-life is 2-3 hours in adults (2.5-3 hours in children). Clinically, dosing every 4-6 hours is needed to maintain therapeutic levels.
Protein binding	10-25% bound to albumin at therapeutic concentrations.
Volume of Distribution	0.8-1.0 L/kg. Indicates distribution into total body water.
Bioavailability	100% (intravenous); not applicable for other routes as OFIRMEV is IV only.
Onset of Action	Intravenous: 5-10 minutes. No oral route for OFIRMEV (IV only).
Duration of Action	4-6 hours (analgesic effect). Clinical note: Duration of antipyresis is shorter, typically 4-6 hours.

Classification & Brands

Dosing & administration

IV: 1000 mg every 6 hours or 650 mg every 4 hours; maximum single dose: 1000 mg; minimum dosing interval: 4 hours; maximum daily dose: 4000 mg.

Dosage form	SOLUTION
Renal impairment	No dose adjustment required for GFR ≥30 mL/min. For GFR <30 mL/min, extend dosing interval to every 8 hours; maximum daily dose 3000 mg.
Liver impairment	Child-Pugh Class A: No adjustment. Child-Pugh Class B: Reduce total daily dose by 50% (max 2000 mg/day). Child-Pugh Class C: Contraindicated or use with extreme caution; reduce dose to 50% of standard and extend interval to every 8 hours; maximum 2000 mg/day.
Pediatric use	Weight-based: <10 kg: 7.5 mg/kg/dose every 6 hours; 10-50 kg: 15 mg/kg/dose every 6 hours; >50 kg: 1000 mg every 6 hours or 650 mg every 4 hours. Maximum single dose: 15 mg/kg (up to 1000 mg); maximum daily dose: 75 mg/kg (up to 4000 mg).
Geriatric use	No specific dose adjustment; consider reduced renal function. For CrCl <30 mL/min, extend interval to every 8 hours. Maximum daily dose: 3000 mg in frail elderly or with comorbidities.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for OFIRMEV (OFIRMEV).

Breastfeeding	Acetaminophen is excreted in breast milk in low concentrations (M/P ratio approximately 0.9-1.0). Considered compatible with breastfeeding; peak milk levels occur 1-2 hours after maternal dosing. Use lowest effective dose for shortest duration.
Teratogenic Risk	Acetaminophen (OFIRMEV) is generally considered low risk across all trimesters. No increased risk of major congenital anomalies has been consistently demonstrated. Chronic high-dose use in third trimester may be associated with preterm birth or low birth weight. Avoid prolonged use above recommended doses.

Warnings & precautions

■ FDA Black Box Warning

Acetaminophen has been associated with cases of acute liver failure, at times resulting in liver transplant and death. Most of the cases of liver injury are associated with the use of acetaminophen at doses that exceed 4000 mg per day, and often involve more than one acetaminophen-containing product.

Side Effect Profile

Serious Effects

Absolute Contraindications

["Known hypersensitivity to acetaminophen or any component of the formulation","Severe hepatic impairment or active liver disease (relative contraindication without black box)"]

Clinical Precautions

Precautions

["Risk of serious hepatotoxicity, especially with doses >4000 mg/day or in patients with underlying liver disease","Risk of severe skin reactions (Stevens-Johnson syndrome, toxic epidermal necrolysis, acute generalized exanthematous pustulosis) – discontinue at first sign of rash","Risk of hypersensitivity reactions including anaphylaxis","Use caution in patients with severe hepatic impairment, active hepatic disease, or alcoholism","Avoid concurrent use of other acetaminophen-containing products"]

Clinical Tips & Counseling

Drug interactions

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OFIRMEV

Clinical safety rating: caution

Comprehensive clinical and safety monograph for OFIRMEV (OFIRMEV).

How it works

What the body does with it

Metabolism	Acetaminophen is primarily metabolized in the liver via conjugation with glucuronide (50-60%) and sulfate (20-30%). A minor amount is oxidized by cytochrome P450 (CYP2E1, CYP1A2, CYP3A4) to a toxic reactive metabolite (NAPQI), which is normally detoxified by glutathione. At toxic doses, glutathione is depleted, leading to NAPQI accumulation and hepatotoxicity.
Excretion	Primarily renal (85% as sulfate and glucuronide conjugates, 10% as unchanged drug). Less than 5% fecal/biliary.
Half-life	Terminal elimination half-life is 2-3 hours in adults (2.5-3 hours in children). Clinically, dosing every 4-6 hours is needed to maintain therapeutic levels.
Protein binding	10-25% bound to albumin at therapeutic concentrations.
Volume of Distribution	0.8-1.0 L/kg. Indicates distribution into total body water.
Bioavailability	100% (intravenous); not applicable for other routes as OFIRMEV is IV only.
Onset of Action	Intravenous: 5-10 minutes. No oral route for OFIRMEV (IV only).
Duration of Action	4-6 hours (analgesic effect). Clinical note: Duration of antipyresis is shorter, typically 4-6 hours.

Classification & Brands

Dosing & administration

IV: 1000 mg every 6 hours or 650 mg every 4 hours; maximum single dose: 1000 mg; minimum dosing interval: 4 hours; maximum daily dose: 4000 mg.

Dosage form	SOLUTION
Renal impairment	No dose adjustment required for GFR ≥30 mL/min. For GFR <30 mL/min, extend dosing interval to every 8 hours; maximum daily dose 3000 mg.
Liver impairment	Child-Pugh Class A: No adjustment. Child-Pugh Class B: Reduce total daily dose by 50% (max 2000 mg/day). Child-Pugh Class C: Contraindicated or use with extreme caution; reduce dose to 50% of standard and extend interval to every 8 hours; maximum 2000 mg/day.
Pediatric use	Weight-based: <10 kg: 7.5 mg/kg/dose every 6 hours; 10-50 kg: 15 mg/kg/dose every 6 hours; >50 kg: 1000 mg every 6 hours or 650 mg every 4 hours. Maximum single dose: 15 mg/kg (up to 1000 mg); maximum daily dose: 75 mg/kg (up to 4000 mg).
Geriatric use	No specific dose adjustment; consider reduced renal function. For CrCl <30 mL/min, extend interval to every 8 hours. Maximum daily dose: 3000 mg in frail elderly or with comorbidities.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for OFIRMEV (OFIRMEV).

Breastfeeding	Acetaminophen is excreted in breast milk in low concentrations (M/P ratio approximately 0.9-1.0). Considered compatible with breastfeeding; peak milk levels occur 1-2 hours after maternal dosing. Use lowest effective dose for shortest duration.
Teratogenic Risk	Acetaminophen (OFIRMEV) is generally considered low risk across all trimesters. No increased risk of major congenital anomalies has been consistently demonstrated. Chronic high-dose use in third trimester may be associated with preterm birth or low birth weight. Avoid prolonged use above recommended doses.

Warnings & precautions

■ FDA Black Box Warning

Side Effect Profile

Serious Effects

Absolute Contraindications

["Known hypersensitivity to acetaminophen or any component of the formulation","Severe hepatic impairment or active liver disease (relative contraindication without black box)"]