OFIRMEV
Clinical safety rating
cautionComprehensive clinical and safety monograph for OFIRMEV (OFIRMEV).
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.
| 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. |
| Molecular Weight | 151.18 |
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. |
| 1st trimester | Avoid use unless clearly needed. Acetaminophen crosses placenta; is considered generally safe at therapeutic doses, but high doses or prolonged use may increase risk of neural tube defects or embryonic toxicity. |
| 2nd trimester | Generally considered safe at therapeutic doses for short-term use. Monitor for maternal hepatotoxicity with prolonged use. |
| 3rd trimester | Generally considered safe; no known risk of premature closure of ductus arteriosus. Limited data on high-dose or prolonged use. |
Clinical note
Comprehensive clinical and safety monograph for OFIRMEV (OFIRMEV).
| Placental transfer | Acetaminophen readily crosses the placenta via passive diffusion; equilibrium between maternal and fetal plasma concentrations is achieved within 30-60 minutes. Concentrations in cord blood are similar to maternal levels. |
| Breastfeeding | Acetaminophen is excreted into breast milk in small amounts (less than 1-2% of maternal dose). Peak milk concentrations occur 1-2 hours after dose. Infant daily exposure is minimal (<1% of therapeutic infant dose). No known adverse effects in breastfed infants at usual maternal doses. Guidelines consider it compatible with breastfeeding. |
| Lactation Rating | L1 (Safe) |
| 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. |
| Fetal Monitoring | No specific fetal monitoring required. Standard obstetric care. Monitor maternal liver function if prolonged high-dose therapy. Consider maternal serum acetaminophen levels if overdose suspected. |
| Fertility Effects | No known adverse effects on male or female fertility at therapeutic doses. |
■ 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.
| Serious Effects |
Active hepatotoxicitySevere hepatic impairment (Child-Pugh Class C)
| 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 |
| Food/Dietary | No known food interactions. However, avoid excessive alcohol consumption as it may increase the risk of liver damage. |
| Clinical Pearls | OFIRMEV (acetaminophen) injection is an IV formulation of acetaminophen used for pain and fever management. It is a prodrug that requires no hepatic conversion, providing rapid onset of action. Monitor for hepatotoxicity; maximum daily dose is 4 grams in adults but lower in patients with hepatic impairment or malnutrition. Do not exceed 1 gram per dose. Hypotension and anaphylaxis have been reported. Not interchangeable with oral acetaminophen due to dose equivalency. Use with caution in patients with alcohol use disorder. |
| Patient Advice | OFIRMEV is given intravenously for pain or fever. · Do not take additional acetaminophen-containing medications while receiving OFIRMEV. · Report any signs of allergic reaction (rash, itching, swelling, trouble breathing). · Seek immediate medical attention if you experience severe abdominal pain, yellowing of skin or eyes, or dark urine. · Inform your healthcare provider about all medications you are taking, especially blood thinners. |
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