Rapid development of numbness of the tongue and choking can occur. In severe cases, excessive absorption can lead to laryngospasm, bronchospasm, seizures, and circulatory collapse. This may be due to a hypersensitivity reaction to benzonatate or a systemic local anesthetic toxicity, both of which have similar symptoms. There is a potential for these adverse effects to occur at a therapeutic dose, that is, a single capsule, if chewed or sucked on in the mouth. Psychiatric effects
Isolated cases of bizarre behavior, mental confusion, and visual hallucinations have been reported during concurrent use with other prescribed medications. Central nervous system effects associated with other para-aminobenozic acid (PABA) derivative local anesthetics, for example procaine or tetracaine, could occur with benzonatate and should be considered. Children
Safety and efficacy in children below the age of 10 have not been established. Accidental ingestion resulting in death has been reported in children below the age of 10. Benzonatate may be attractive to children due to its appearance, a round-shaped liquid-filled gelatin capsule, which looks like candy. Chewing or sucking of a single capsule can cause death of a small child. Signs and symptoms can occur rapidly after ingestion (within 15–20 minutes) and include restlessness, tremors, convulsions, coma, and cardiac arrest. Death has been reported within one hour of ingestion. Pregnancy and breast feeding
In the U.S., benzonatate is classified by the U.S. Food and Drug Administration (FDA) as pregnancy category C. It is not known if benzonatate can cause fetal harm to a pregnant woman or if it can affect reproduction capacity.
Certain combinations of mutations in the given progenitor cell ultimately result in that cell (also called a cancer stem cell) displaying a number of abnormal, malignant cellular properties that, when taken together, are considered characteristic of cancer, including:

the ability to continue to divide perpetually, producing an exponentially (or near-exponentially) increasing number of new malignant cancerous "daughter cells" (uncontrolled mitosis);
the ability to penetrate normal body surfaces and barriers, and to bore into or through nearby body structures and tissues (local invasiveness);
the ability to spread to other sites within the body (metastasize) by penetrating or entering into the lymphatic vessels (regional metastasis) and/or the blood vessels (distant metastasis).If this process of continuous growth, local invasion, and regional and distant metastasis is not halted via a combination of stimulation of immunological defenses and medical treatment interventions, the result is that the host has a continuously increasing burden of tumor cells throughout the body. Eventually, the tumor burden increasingly interferes with normal biochemical functions carried out by the hosts organs, and death ultimately ensues. Carcinoma is but one form of cancer—one composed of cells that have developed the cytological appearance, histological architecture, or molecular characteristics of epithelial cells. A progenitor carcinoma stem cell can be formed from any of a number of oncogenic combinations of mutations in a totipotent cell, a multipotent cell, or a mature differentiated cell.