Generic Name

Dexchlorpheniramine Maleate

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Classification

FDA Approved Indications

• Relief of allergic symptoms such as hay fever, conjunctivitis, allergic rhinitis, urticaria, and other allergic skin conditions

Mechanism of Action

Dexchlorpheniramine competitively blocks H1 receptors on effector cells in the gastrointestinal tract, blood vessels, and respiratory tissues, thereby counteracting the effects of endogenous histamine.

Dosage and Administration

Adult: Typically 4 mg every 4 to 6 hours as needed, not exceeding 24 mg per day

Pediatric: 2-4 mg every 4 to 6 hours, with a maximum of 12-24 mg per day depending on age and weight

Geriatric: Start at lower doses due to increased sensitivity and risk of anticholinergic effects

Renal Impairment: Use with caution; dose adjustments may be necessary based on renal function

Hepatic Impairment: Use with caution; monitor for increased adverse effects; no specific dose adjustment established

Pharmacokinetics

Absorption: Well absorbed from the gastrointestinal tract

Distribution: Widely distributed in body tissues; crosses the blood-brain barrier, causing sedative effects

Metabolism: Partially metabolized in the liver

Excretion: Excreted primarily in urine

Half Life: About 14 hours, but may be prolonged in renal impairment

Contraindications

• Known hypersensitivity to dexchlorpheniramine or other antihistamines
• Use in neonates or premature infants

Precautions

• May cause drowsiness; caution with activities requiring alertness
• Prostate hypertrophy, glaucoma, hypertension, cardiovascular disease, bronchial asthma, hyperthyroidism, peptic ulcer, or urinary retention

Adverse Reactions - Common

• Drowsiness, dry mouth, dizziness, blurred vision (Common)
• Gastrointestinal disturbances (Uncommon)

Adverse Reactions - Serious

• Anticholinergic effects such as urinary retention, hallucinations, or seizures (Rare)
• Allergic reactions including rash, pruritus, or anaphylaxis (Rare)

Drug-Drug Interactions

• CNS depressants (additive sedation)
• Monoamine oxidase inhibitors (antihistaminic effects may be potentiated)

Drug-Food Interactions

N/A

Drug-Herb Interactions

N/A

Nursing Implications

Patient/Family Teaching

• Avoid driving or operating machinery until response is known
• Warn about drowsiness and the potential for impairment
• Instruct on avoiding alcohol and other CNS depressants
• Report any signs of allergic or adverse reactions

Special Considerations

Black Box Warnings:

• None currently

Genetic Factors: Pharmacogenomics related to CYP450 metabolism may influence drug levels (not specifically established)

Lab Test Interference: May cause false-positive results for certain diagnostic tests such as urinary catecholamines or antinuclear antibodies

Overdose Management

Signs/Symptoms: Anticholinergic toxicity, agitation, hallucinations, seizures, coma

Treatment: Supportive care, activated charcoal if ingestion was recent, thermoregulation, and symptomatic management. Physostigmine may be used in certain cases under supervision.

Storage and Handling

Storage: Store at room temperature, away from light and moisture

Stability: Stable under recommended storage conditions for the duration of the shelf life