recommended to exercise caution when benzonatate is given to a nursing woman. Overdose Benzonatate is chemically similar to other local anesthetics such as tetracaine and procaine, and shares their pharmacology and toxicology. Benzonatate overdose is characterized by symptoms of restlessness, tremors, seizures, abnormal heart rhythms (cardiac arrhythmia), cerebral edema, absent breathing (apnea), fast heart beat (tachycardia), and in severe cases, coma and death. Symptoms develop rapidly, typically within 1 hour of ingestion. Treatment focuses on removal of gastric contents and on managing symptoms of sedation, convulsions, apnea, and cardiac arrhythmia. Despite a long history of safe and appropriate usage, the safety margin of benzonatate is reportedly narrow. Toxicity above the therapeutic dose is relatively low and ingestion of a small handful of pills can cause symptoms of overdose. Children are at an increased risk for toxicity, which have occurred with administration of only one or two capsules. Due to increasing usage of benzonatate and rapid onset of symptoms, there are accumulating cases of benzonatate overdose deaths, especially in children. Pharmacology Benzonatate is chemically similar to other local anesthetics such as tetracaine and procaine, and shares their pharmacology. Mechanism of action Similar to other local anesthetics, benzonatate is a potent voltage-gated sodium channel inhibitor. After absorption and circulation to the respiratory tract, benzonatate acts as a local anesthetic, decreasing the sensitivity of vagal afferent fibers and stretch receptors in the bronchi, alveoli, and pleura in the lower airway and lung. This damps their activity and reduces the cough reflex. Benzonatate also has central antitussive activity on the cough center in central nervous system at the level of the medulla. However, there is minimal inhibition of the respiratory center at a therapeutic dosage. Pharmacokinetics The antitussive effect of benzonatate begins within 15 to 20 minutes after oral administration and typically lasts between 3 and 8 hours. Benzonatate is hydrolyzed by plasma butyrylcholinesterase (BChE) to the metabolite 4-(butylamino)benzoic acid (BABA) as well as polyethylene glycol monomethyl esters. Like many other local anesthetic esters, the hydrolysis of the parent compound is rapid. There are concerns that those with pseudocholinesterase deficiencies may have an increased sensitivity to benzonatate as this hydrolysis is impaired, leading to increased levels of circulating medication. Chemical structure Benzonatate is a butylamine, structurally related to other polyglycol ester local anesthetics such as procaine and tetracaine. The molecular weight of benzonatate is 603.7 g/mol. However, the reference standard for benzonatate is a