Piriton (Chlorpheniramine) Dosage
For adults and children 12 years and older, take one 4 mg tablet every 4 to 6 hours, not exceeding 6 tablets (24 mg) in 24 hours; for children 6 to under 12 years, give half a tablet (2 mg) every 4 to 6 hours, not exceeding 3 half-tablets (6 mg) in 24 hours. 1
Standard Dosing by Age
Adults and children ≥12 years:
- Dose: 4 mg orally every 4-6 hours 1
- Maximum: 24 mg per 24 hours (6 tablets) 1
- Timing: Can be taken earlier in the day if sedation is a concern, though this is more relevant for stimulant medications 1
Children 6 to <12 years:
Children <6 years:
- Not recommended for use 1
Important Pharmacokinetic Considerations
The elimination half-life of chlorpheniramine is approximately 23-28 hours in adults, which is considerably longer than the traditional 4-6 hour dosing interval suggests. 2 This long half-life means:
- Significant drug accumulation occurs with frequent dosing (every 4-6 hours), with accumulation ratios ranging from 4.1 to 9.4 (mean 6.5) 2
- Steady-state is reached after approximately 6 days of regular dosing 3
- Less frequent dosing may be appropriate for many patients, particularly adults, though the FDA-approved labeling maintains the traditional 4-6 hour interval 1, 2
Formulation Details
Each standard tablet contains 4 mg chlorpheniramine maleate as the active ingredient. 1
Clinical Pitfalls
Avoid chronic frequent dosing without consideration of accumulation: The traditional every 4-6 hour dosing schedule, when followed strictly, leads to substantial drug accumulation due to the 24+ hour half-life. 2 Monitor for excessive sedation or anticholinergic effects (dry mouth, urinary retention, confusion) especially in elderly patients or those on multiple medications.
Bioavailability varies significantly: Oral bioavailability ranges from 25-59% due to extensive first-pass hepatic metabolism, meaning individual patient response may vary. 2