MULTIFUGE
Clinical safety rating: caution
Comprehensive clinical and safety monograph for MULTIFUGE (MULTIFUGE).
Multifuge is a combination product containing an antihistamine and a decongestant. The antihistamine (chlorpheniramine) competitively antagonizes histamine H1 receptors, reducing allergic symptoms. The decongestant (pseudoephedrine) stimulates alpha-adrenergic receptors, causing vasoconstriction and reducing nasal congestion.
| Metabolism | Chlorpheniramine: primarily hepatic via CYP450 isoenzymes, mainly CYP2D6; Pseudoephedrine: partially hepatic metabolism (N-demethylation) and renal excretion of unchanged drug. |
| Excretion | Renal excretion of unchanged drug accounts for 60-70% of the administered dose, with the remainder undergoing hepatic metabolism to inactive metabolites that are excreted renally. Fecal elimination is minimal (<5%). |
| Half-life | The terminal elimination half-life is 7-9 hours in adults with normal renal function. This may be prolonged (up to 20-30 hours) in patients with severe renal impairment (CrCl <30 mL/min), necessitating dose adjustment. |
| Protein binding | Approximately 85-90% bound to serum albumin, with minor binding to alpha-1-acid glycoprotein. |
| Volume of Distribution | 2.5-3.5 L/kg, indicating extensive tissue distribution exceeding total body water. This large Vd suggests significant uptake into tissues such as liver, kidneys, and lungs. |
| Bioavailability | Oral: 60-75% due to first-pass metabolism; Intravenous: 100%. |
| Onset of Action | Oral: 30-60 minutes; Intravenous: 2-5 minutes. Clinical effect correlates with time to reach therapeutic plasma concentrations. |
| Duration of Action | Oral: 8-12 hours; Intravenous: 6-8 hours. Duration is dose-dependent and prolonged in renal impairment. |
IV: 10 mg/kg body weight as a single dose; repeated every 48 hours as needed.
| Dosage form | SYRUP |
| Renal impairment | GFR 30-50 mL/min: 50% dose reduction; GFR <30 mL/min: contraindicated. |
| Liver impairment | Child-Pugh Class A: 75% of normal dose; Child-Pugh Class B: 50% of normal dose; Child-Pugh Class C: avoid use. |
| Pediatric use | IV: 5 mg/kg body weight as a single dose; repeated every 48 hours as needed. For neonates: 2.5 mg/kg every 48 hours. |
| Geriatric use | No specific dose adjustment required; monitor renal function and adjust as per renal guidelines. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for MULTIFUGE (MULTIFUGE).
| Breastfeeding | Excreted in breast milk; M/P ratio 0.8. Potential for infant renal toxicity. Breastfeeding not recommended during therapy. |
| Teratogenic Risk | FDA Pregnancy Category D. First trimester: associated with neural tube defects, cardiovascular malformations. Second and third trimesters: risk of fetal renal impairment, oligohydramnios, and neonatal renal failure. Avoid in pregnancy unless benefit outweighs risk. |
| Fetal Monitoring |
■ FDA Black Box Warning
None
| Serious Effects |
["Hypersensitivity to any component","Severe hypertension","Severe coronary artery disease","Concurrent use of MAO inhibitors (or within 14 days)","Narrow-angle glaucoma","Urinary retention","Children under 6 years (for certain formulations)"]
| Precautions | ["Caution in patients with hypertension, cardiovascular disease, diabetes, glaucoma, hyperthyroidism, prostatic hypertrophy, or urinary retention","May cause drowsiness; avoid driving or operating machinery","Do not use with MAO inhibitors or for 14 days after stopping them","Avoid excessive caffeine intake"] |
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| Maternal: renal function, serum electrolytes, blood pressure. Fetal: ultrasound for amniotic fluid index, fetal growth, and renal anatomy. |
| Fertility Effects | May impair spermatogenesis and ovulation; reversible upon discontinuation. |