Piriton (Chlorphenamine) Dosing
For adults and children over 12 years, administer 10 mg IM or IV slowly; for children 6-12 years, give 5 mg; for children 6 months to 6 years, give 2.5 mg; and for infants under 6 months, give 250 µg/kg. 1
Standard Dosing by Age Group
The dosing of chlorphenamine (Piriton) follows a straightforward age-based algorithm that does not require adjustment for renal or hepatic impairment in the acute setting:
Adults and Adolescents
- >12 years: 10 mg administered intramuscularly or intravenously slowly 1
- This represents the maximum single dose for this age group in the context of anaphylaxis management
Pediatric Dosing
- 6-12 years: 5 mg IM or IV slowly 1
- 6 months to 6 years: 2.5 mg IM or IV slowly 1
- <6 months: 250 µg/kg IM or IV slowly 1
Administration Considerations
Intravenous administration must be performed slowly to minimize adverse effects. 1 The guideline specifically emphasizes slow IV push when using this route, which is critical for preventing hypotension or other acute reactions.
Pharmacokinetic Properties
Chlorphenamine has a long elimination half-life that supports less frequent dosing than traditionally prescribed. 2 A bioequivalence study demonstrated that the elimination half-life allows for dosing intervals of 4-6 hours or longer in adults, rather than the more frequent dosing sometimes recommended. 2 This pharmacokinetic profile means that repeat dosing should be spaced appropriately to avoid accumulation.
Clinical Context
These doses are derived from anaphylaxis management guidelines, where chlorphenamine serves as an adjunctive H1-antihistamine alongside epinephrine and corticosteroids. 1 The medication is administered after initial resuscitation with epinephrine has been initiated. 1
Important Caveats
No specific dose adjustments are provided in the guideline for renal or hepatic impairment in the acute anaphylaxis setting. 1 The standard age-based dosing applies regardless of organ function when treating acute allergic reactions. This differs from chronic dosing scenarios where accumulation might be a concern, but in the acute emergency context, the immediate benefit outweighs theoretical risks of single-dose administration in patients with organ dysfunction.
The weight-based dosing for infants (<6 months) requires careful calculation at 250 µg/kg to avoid dosing errors. 1 This is the only age group where weight-based rather than fixed dosing is specified.