Benzonatate Overdose Presenting as Cardiac Arrest with Rapidly Narrowing QRS Interval
Robert J Stephens1, Ari B Filip2, Kevin T Baumgartner2
1Department of Emergency Medicine, Barnes-Jewish Hospital, Washington University School of Medicine in Saint Louis, 660 Euclid Avenue, Saint Louis, MO, 63110 CB #8072, USA. stephensr@wustl.edu.
Summary
Benzonatate overdose can cause cardiac arrest and QRS prolongation, but it may resolve rapidly. A normal ECG does not rule out benzonatate toxicity.
Area of Science:
- Toxicology
- Cardiology
- Pharmacology
Background:
- Benzonatate, a common antitussive, acts as a local anesthetic and sodium channel antagonist.
- Overdoses can lead to significant cardiovascular toxicity, including arrhythmias and altered QRS duration.
Observation:
- A 14-year-old patient presented with cardiac arrest after a benzonatate overdose.
- Initial ECG showed sinus rhythm with a prolonged QRS of 160 ms, which rapidly normalized to 94 ms within 44 minutes.
- Urine benzonatate concentration confirmed exposure.
Findings:
- This case demonstrates transient QRS prolongation in benzonatate overdose, consistent with sodium channel blockade.
- Rapid normalization of QRS duration occurred despite initial severe toxicity.
Implications:
- Transient QRS prolongation on ECG should not exclude benzonatate overdose as a diagnosis.
- Clinicians should consider benzonatate toxicity in patients with cardiac arrest and altered QRS intervals, even with rapid ECG resolution.
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