Chlorpheniramine (Chlorpheniramine maleate) Toxicity Threshold by Oral Dose
No single oral dose in mg is considered universally “toxic” because toxicity severity varies by patient factors and formulation. Estimated lethality for chlorpheniramine/chlorphenamine is reported as 25 to 50 mg/kg body weight by oral route. [1]
Evidence for Toxic/Lethal Dose Estimates
- A UK Summary of Product Characteristics for chlorphenamine (chlorpheniramine) reports an estimated lethal dose of 25 to 50 mg/kg (oral). [1]
- Published case literature includes severe poisoning with an oral dose of 4000 mg, described as the highest reported poisoning dose in that report. [2]
Practical Dose Translation (Using mg/kg)
- For an adult weighing 70 kg, an estimated lethal range based on 25–50 mg/kg corresponds to 1750 to 3500 mg of chlorpheniramine. [1]
Overdose Actions
- In suspected chlorpheniramine overdose, Poison Help is reachable at 1-800-222-1222 in the United States. [3]
- Emergency evaluation is warranted for any suspected significant antihistamine overdose because CNS effects (eg, seizures, delirium) can occur. [2]
Sources
[1] Chlorphenamine 4mg tablets - SmPC (emc).
[2] Chlorpheniramine poisoning as a potential cause of rhabdomyolysis (case report).
[3] MedlinePlus Drug Information for chlorpheniramine (overdose guidance).