DEXCHLORPHENIRAMINE MALEATE
Clinical safety rating: caution
Comprehensive clinical and safety monograph for DEXCHLORPHENIRAMINE MALEATE (DEXCHLORPHENIRAMINE MALEATE).
Dexchlorpheniramine maleate is a histamine H1 receptor antagonist that competitively blocks the effects of histamine at peripheral H1 receptors, reducing symptoms of allergic reactions such as vasodilation, increased vascular permeability, and smooth muscle contraction. It also has anticholinergic and sedative properties.
| Metabolism | Primarily hepatic via CYP450 enzymes, mainly CYP2D6. Metabolites are excreted renally. |
| Excretion | Primarily renal (approximately 70-80% as unchanged drug and metabolites, mainly glucuronide conjugates); minor biliary/fecal elimination (20-30%). |
| Half-life | Terminal elimination half-life is 20-24 hours in healthy adults, allowing once or twice daily dosing. Prolonged in hepatic impairment or elderly. |
| Protein binding | Approximately 70-80% bound to serum albumin; reversible binding. |
| Volume of Distribution | Reported as 2.5-3.5 L/kg, indicating extensive tissue distribution (larger than total body water). |
| Bioavailability | Oral: approximately 40-60% due to first-pass metabolism. IM/IV: 100%. |
| Onset of Action | Oral: 30-60 minutes. Intramuscular: 15-30 minutes. Intravenous: 1-5 minutes. |
| Duration of Action | Antihistaminic effect lasts 24 hours due to long half-life. CNS depressant effects may persist longer; avoid concurrent alcohol or sedatives. |
2 mg orally every 4-6 hours; maximum 12 mg/day
| Dosage form | TABLET |
| Renal impairment | eGFR 30-50 mL/min: administer every 6-8 hours; eGFR <30 mL/min: administer every 8-12 hours |
| Liver impairment | Child-Pugh class A: no adjustment; Child-Pugh class B or C: use with caution, consider dose reduction or extended interval |
| Pediatric use | 6-12 years: 1 mg orally every 4-6 hours (max 6 mg/day); 2-5 years: 0.5 mg orally every 4-6 hours (max 3 mg/day); <2 years: not recommended |
| Geriatric use | Initiate at 1 mg orally every 6 hours; monitor for anticholinergic effects and sedation; avoid in patients with cognitive impairment or glaucoma |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for DEXCHLORPHENIRAMINE MALEATE (DEXCHLORPHENIRAMINE MALEATE).
| Breastfeeding | Excreted into breast milk in small amounts; M/P ratio unknown. Use with caution; consider risk of infant sedation or irritability. American Academy of Pediatrics considers compatible but prefer non-sedating alternatives. |
| Teratogenic Risk | First trimester: Insufficient human data; animal studies show no teratogenicity. Second/third trimester: Use not recommended near term due to potential for respiratory depression, irritability, or paradoxical CNS stimulation in neonates. |
■ FDA Black Box Warning
None
| Serious Effects |
["Hypersensitivity to dexchlorpheniramine or any component of the formulation","Neonates and premature infants","Nursing mothers","Concomitant use with monoamine oxidase inhibitors (MAOIs)"]
| Precautions | ["Caution in elderly patients due to increased sensitivity to anticholinergic effects (e.g., confusion, urinary retention).","Avoid use in patients with narrow-angle glaucoma, symptomatic prostatic hypertrophy, bladder neck obstruction, pyloroduodenal obstruction, or stenosing peptic ulcer.","May cause drowsiness; caution when driving or operating machinery.","Use caution in patients with asthma, chronic obstructive pulmonary disease, or other lower respiratory tract diseases.","Avoid concurrent use with alcohol or other CNS depressants."] |
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| Fetal Monitoring |
| Monitor maternal sedation, anticholinergic effects, and fetal heart rate if used near delivery. No specific drug level monitoring required. |
| Fertility Effects | No known adverse effects on human fertility; animal data show no impairment. |