Chlorpheniramine Maleate



Chlor-Trimeton, Aller-Chlor


  • Tablets: 4 mg
  • Syrup: 2 mg/5mL, 0.4 mg/mL


An alkylamine derivative, this drug is among the most potent of antihistamines but unlike the ethanolamine derivatives is only minimally sedative. Like other antihistaminics it blocks histamine at the receptor site.

It is well absorbed orally and distributed in high levels to spleen, lungs, and brain. It is able to cross the placental barrier.

The drug is metabolized in the liver and excreted as metabolites in urine and breast milk.


Used where allergy symptoms, or nasal congestion are present.

Drug Interactions or Contraindications:

  • Use cautiously with central nervous system depressants as it can increase sedative effect.
  • Do not use for acute asthmatic attacks.
  • Not recommended to be given to pregnant or lactating rats.

Adverse Reactions

CNS: drowsy, poor coordination, tonic/clonic seizures

CV: palpitations

GI: dry mouth, diarrhea, constipation

GU: urine retention

Other: maycause thick bronchial secretions

Dosage Recommendations

0.2 mg/lb, PO, BID, for allergy/respiratory symptoms  12


0.6 mg/kg, PO, q24hr  42


  • Can be purchased over the counter.
  • Give lots of fluids to decrease bronchial secretion viscosity.
  • Avoid milk products.
  • Give with food to avoid GI reactions.
  • Store drug at room temperature.


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