Brompheniramine and Adverse CNS/Cardiovascular Effects
Yes, brompheniramine can cause both hallucinations and elevated heart rate, particularly in overdose situations, though these effects can occasionally occur even at therapeutic doses. 1
Hallucinations and CNS Effects
Brompheniramine, as a first-generation antihistamine with anticholinergic properties, can produce significant central nervous system effects:
CNS effects from brompheniramine overdosage may vary from depression to stimulation, especially in children, with anticholinergic effects being notable. 1 This spectrum of effects means that while sedation is common, paradoxical stimulation and hallucinations can occur.
The FDA drug label explicitly warns that CNS stimulation can manifest as hallucinations, particularly when toxic doses are ingested or in susceptible individuals. 1
In clinical trials at therapeutic doses, CNS-related complaints including somnolence and confusion were reported, with one documented case of confusion during treatment. 2, 3
Tachycardia and Cardiovascular Effects
Brompheniramine can cause elevated heart rate through multiple mechanisms:
When combined with pseudoephedrine (a common formulation), toxic doses may result in tachycardia, hypertension, and cardiac arrhythmias. 1 Even brompheniramine alone has cardiovascular effects.
Electrophysiological studies demonstrate that brompheniramine affects cardiac ion channels, including sodium and calcium channels, which can alter heart rate and rhythm. 4 At concentrations of 21.26 μM for sodium channels and 16.12 μM for calcium channels, significant inhibition occurs.
In overdose cases of the related antihistamine diphenhydramine, mean heart rate was significantly elevated at 103 ± 25 beats/min compared to normal. 5 Similar mechanisms apply to brompheniramine given their shared anticholinergic properties.
Clinical Context and Risk Factors
Children are particularly susceptible to CNS stimulation effects, while adults more commonly experience CNS depression. 1 This age-related difference is critical for anticipating which adverse effects are most likely.
The severity of these effects is dose-dependent:
A 2½-year-old child survived ingestion of 300-900 mg of brompheniramine, demonstrating that even massive overdoses can be survived with appropriate supportive care. 1
Therapeutic doses (12 mg twice daily) primarily cause somnolence rather than stimulation or tachycardia in most patients. 2, 3
Management Considerations
If brompheniramine toxicity with hallucinations or tachycardia is suspected:
Induce emesis only if the patient is alert and presents within 6 hours of ingestion, with precautions against aspiration. 1
For CNS hyperactivity or convulsive seizures, intravenous short-acting barbiturates may be indicated. 1
Hypertensive responses and/or tachycardia should be treated appropriately with standard antihypertensive or rate-control measures. 1
Supportive care with oxygen, intravenous fluids, and monitoring remains the cornerstone of management. 1
Important Caveats
The combination of brompheniramine with sympathomimetics like pseudoephedrine significantly increases the risk of tachycardia and hypertension. 1 Always clarify whether the patient ingested brompheniramine alone or in a combination product, as this substantially changes the risk profile and expected cardiovascular effects.
While QTc prolongation has been documented with brompheniramine (mean 453 ± 43 ms in overdose), torsades de pointes has not been reported, unlike with second-generation antihistamines. 4, 5 This suggests a different risk profile despite the cardiac ion channel effects.