Benzonatate, often prescribed as Tessalon Perles, is a non-narcotic prescription medication used to relieve and suppress cough. This drug is contained within a liquid-filled capsule designed to be swallowed whole and intact. The capsule must never be chewed, sucked, or dissolved in the mouth. Improper use, even accidental, can lead to the rapid onset of severe, potentially life-threatening reactions.
Benzonatate’s Mechanism of Action When Used Correctly
When swallowed, benzonatate capsules pass into the gastrointestinal tract and are absorbed into the bloodstream. The drug travels to target sites within the respiratory system, acting as a local anesthetic similar to agents like procaine.
The medication desensitizes the peripheral sensory nerve receptors involved in the cough reflex. It targets the stretch receptors located in the lungs, respiratory passages, and the pleura (the membrane lining the lungs). By numbing these receptors, benzonatate diminishes the signals sent through the vagal nerve to the cough center in the brain’s medulla. This action raises the threshold required to trigger a cough, providing relief without suppressing the respiratory center.
Why Chewing Triggers Immediate Localized Reactions
Chewing or dissolving the capsule instantly releases the potent liquid anesthetic directly onto the oral and pharyngeal mucous membranes. This high-concentration exposure causes dangerous localized effects. The initial consequence is a rapid, intense numbing sensation affecting the tongue, mouth, throat, and esophagus.
This localized anesthesia presents a serious physical danger. The numbness can impair the function of muscles responsible for swallowing and airway protection, creating a risk of choking or aspirating food or liquid into the lungs. The localized effect can also trigger severe hypersensitivity reactions, including laryngospasm (a sudden constriction of the vocal cords) and bronchospasm (a tightening of the muscles around the airways). Both reactions severely compromise the ability to breathe.
Recognizing Systemic Toxicity and Emergency Response
Chewing benzonatate creates danger far beyond the localized numbing of the throat. When the anesthetic is released prematurely, a large amount of the drug is rapidly absorbed through the mucous membranes into the systemic circulation. This bypasses the normal digestive process and quickly leads to toxic levels in the bloodstream, resulting in severe central nervous system (CNS) and cardiovascular toxicity.
Symptoms of systemic toxicity can manifest rapidly, often within 15 to 20 minutes of chewing the capsule. Initial signs of CNS involvement include restlessness, tremors, confusion, and disorientation, as the drug disrupts normal nerve signaling. This can quickly escalate to severe neurological events, such as convulsions and seizures.
The cardiovascular system is vulnerable to the anesthetic’s effects, which inhibit the electrical activity of the heart. Overdose can lead to profound cardiovascular depression, manifesting as a slow heart rate, weak pulse, and a rapid drop in blood pressure. This can result in cardiac arrest. Because these reactions are severe and have been fatal, especially in children, accidental chewing must be treated as a medical emergency.
Immediate action is mandatory if a capsule is chewed or if any signs of numbness, confusion, or breathing difficulty are observed. Deterioration can be rapid and irreversible, so do not wait for severe symptoms to develop. The individual requires immediate medical intervention; calling 911 or a local Poison Control Center is the appropriate response. There is no specific antidote for benzonatate toxicity, so treatment focuses on managing symptoms and providing aggressive supportive care without delay.