Injectable Chlorpheniramine Maleate Dosing for Children
The recommended injectable chlorpheniramine maleate dose for children is weight and age-based: children >12 years receive 10 mg IM or IV slowly, 6-12 years receive 5 mg, 6 months to 6 years receive 2.5 mg, and infants <6 months receive 250 µg/kg. 1
Age-Based Dosing Algorithm
The dosing follows a clear stepwise approach based on age groups 1:
- Children >12 years: 10 mg IM or IV (administered slowly)
- Children 6-12 years: 5 mg IM or IV (administered slowly)
- Children 6 months to 6 years: 2.5 mg IM or IV (administered slowly)
- Infants <6 months: 250 µg/kg IM or IV (administered slowly)
Clinical Context and Administration
This dosing guideline is specifically established for anaphylactic reactions associated with anaesthesia, where chlorpheniramine serves as an adjunctive treatment alongside epinephrine and hydrocortisone 1. The medication should be administered either intramuscularly or intravenously with slow infusion to minimize adverse effects 1.
Important Administration Considerations
- Route flexibility: Both IM and IV routes are acceptable, with IV administration requiring slow infusion 1
- Weight-based dosing for infants: The youngest age group (<6 months) uniquely requires calculation based on body weight rather than a fixed dose, reflecting their greater pharmacokinetic variability 1
- Pharmacokinetic differences in children: Chlorpheniramine clearance in children (234-470 ml/hr/kg) is approximately twofold variable and generally decreases with age, with a shorter elimination half-life (mean 9.6 hours) compared to adults 2
Critical Safety Considerations
Avoid confusion with pheniramine maleate: The question asks about "pheniramine maleate," but the evidence and standard clinical practice refer to chlorpheniramine maleate—these are different antihistamines. Chlorpheniramine is the first-generation H1 antihistamine with established pediatric dosing guidelines 1, 3.
Common Pitfalls
- Do not extrapolate adult dosing: Children have distinct pharmacokinetic profiles with higher clearance rates requiring age-appropriate dosing 2
- Sedation risk: Sedation is the most commonly reported adverse effect and appears more prevalent in younger children (2-5 years), though this data primarily reflects oral administration 4
- Slow IV administration is mandatory: Rapid IV injection may increase risk of adverse cardiovascular effects 1