What are the side effects of benzonate?

Side Effects of Benzonatate

Benzonatate can cause serious and potentially fatal adverse effects, particularly hypersensitivity reactions, CNS toxicity including seizures and hallucinations, and cardiovascular complications including cardiac arrest—with death reported within one hour of overdose, especially in children. 1

Common Side Effects

The FDA-approved labeling identifies the following potential adverse reactions to benzonatate:

• CNS effects: Sedation, headache, dizziness, mental confusion, and visual hallucinations 1
• Gastrointestinal effects: Constipation, nausea, and GI upset 1
• Dermatologic effects: Pruritus and skin eruptions 1
• Other effects: Nasal congestion, sensation of burning in the eyes, vague "chilly" sensation, numbness of the chest, and hypersensitivity 1

Serious and Life-Threatening Side Effects

Hypersensitivity Reactions

• Severe hypersensitivity reactions can occur, including bronchospasm, laryngospasm, and cardiovascular collapse, particularly when the capsule is chewed or sucked instead of swallowed (which causes local anesthesia) 1
• These severe reactions may require vasopressor agents and supportive measures 1

Cardiovascular Toxicity

• Cardiac arrest is a documented serious adverse effect, occurring rapidly after overdose 1, 2, 3
• Dysrhythmias including torsades de pointes have been reported in overdose cases 3, 4
• Benzonatate has sodium channel blocking properties similar to local anesthetics like tetracaine and procaine, contributing to its cardiotoxic effects 5, 2

Neurologic Toxicity

• Seizures are a common manifestation of benzonatate toxicity 5, 4
• Coma and CNS depression can occur 5, 4
• Isolated instances of bizarre behavior, mental confusion, and visual hallucinations have been reported, particularly when benzonatate is taken in combination with other prescribed drugs 1

Critical Safety Warnings

Accidental Ingestion in Children

• Death has been reported in children below age 10 following accidental ingestion 1
• Signs and symptoms of overdose can appear within 15-20 minutes, and death has been reported within one hour of ingestion 1, 6
• Five fatalities occurred from accidental ingestions in children 2 years of age and younger 6
• Benzonatate must be kept out of reach of children 1

Overdose Characteristics

• Intentional exposures carry significantly higher risk: 22% experienced serious adverse effects and 38% required hospitalization 5
• Unintentional exposures rarely cause serious toxicity: only 0.7% experienced serious adverse effects 5
• In a 20-year review, two deaths (0.8%) occurred, both from intentional exposures 5
• Onset of toxicity is rapid (often <5 minutes), with common manifestations including cardiac arrest (29/36 cases), seizures (24/36), and dysrhythmias (24/36) 4
• Most resuscitated patients have significant neurologic deficits or end-organ damage, with only 5 of 23 patients achieving return of spontaneous circulation surviving with good neurologic outcomes 4

Clinical Pitfalls

• No standard treatment guidelines exist for managing benzonatate toxicity; treatment is primarily supportive 5
• The duration of directly toxic effects is short but dramatic, often resulting in neurologic devastation even in resuscitated patients 4
• Rational prescribing and thorough patient education about proper use (swallowing capsules whole, not chewing or sucking) and safe storage are essential 2, 6