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. |
| Molecular Weight | 390.87 |
| Action Class | First-generation alkylamine antihistamine |
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 | Avoid use during first trimester due to potential teratogenicity risk, though data are limited. |
| 2nd trimester | Use with caution; risk-benefit assessment required. Some studies suggest possible association with prematurity. |
| 3rd trimester | Avoid near term due to risk of respiratory depression and withdrawal symptoms in neonate. |
Clinical note
Comprehensive clinical and safety monograph for DEXCHLORPHENIRAMINE MALEATE (DEXCHLORPHENIRAMINE MALEATE).
| Placental transfer | Passes placenta; transferred to fetus detected in cord blood. |
| Breastfeeding | Excreted into breast milk in low amounts; however, may cause irritability, drowsiness, or other anticholinergic effects in nursing infants. Use only if clearly needed and monitor infant for adverse effects. |
■ FDA Black Box Warning
None
| Common Effects | Drowsiness, Sedation, Dizziness, Dry mouth, nose, and throat, Blurred vision, Urinary retention, Constipation, Gastrointestinal upset |
| Serious Effects | Respiratory depression (especially in overdose or with CNS depressants), Seizures, Cardiac arrhythmias (e.g., QT prolongation, torsades de pointes), Severe hypotension, Acute dystonic reactions, Anaphylaxis |
Hypersensitivity to dexchlorpheniramine or other antihistaminesSevere liver diseaseNarrow-angle glaucomaSymptomatic prostatic hypertrophyBladder neck obstructionPyloroduodenal obstructionConcomitant 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. |
Loading safety data…
| Lactation Rating |
| L3 (Moderately Safe) – limited data, use with caution. |
| 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. |
| 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. |
| Food/Dietary | Avoid alcohol consumption. Grapefruit juice may increase systemic exposure, although clinical significance is unclear. High-fat meals may delay absorption, but overall bioavailability remains unaffected. Maintain adequate fluid intake to minimize anticholinergic effects like dry mouth and constipation. |
| Clinical Pearls | Dexchlorpheniramine maleate is a first-generation alkylamine antihistamine with strong antihistaminic and weak anticholinergic properties. It is more potent and less sedating than chlorpheniramine, but sedation and anticholinergic effects still occur. Due to its long half-life (20–24 hours), it can be dosed twice daily. Avoid in patients with angle-closure glaucoma, urinary retention, or asthma exacerbations. Use caution in elderly due to increased sensitivity to anticholinergic effects and risk of cognitive decline. |
| Patient Advice | Take exactly as prescribed; do not exceed recommended dose. · Avoid driving or operating heavy machinery until you know how this drug affects you, as it may cause drowsiness. · Do not consume alcohol or other CNS depressants (e.g., sedatives, tranquilizers) while taking this medication. · Report any signs of urinary difficulty, blurred vision, or rapid heartbeat to your healthcare provider. · For dry mouth, use sugarless gum or candy, and maintain good oral hygiene. · Store at room temperature away from moisture and heat. · Do not use with other antihistamines, including those in over-the-counter cold or allergy products. · If pregnant, planning to become pregnant, or breastfeeding, consult your healthcare provider before use. |