Lidocaine and benzocaine are both local anesthetics, meaning they cause a specific area of the body to be insensitive to pain without causing loss of consciousness2。As local anesthetics, they are commonly used in dental treatments, topical applications and even some surgical procedures.Although they are similar in their modes of action within the body, they are also different in their structure and potency2。

General Properties

Local anesthetics block the sodium (NA+) channels of the cell membranes. By blocking the ability of the sodium channels to open, or become active, the membrane cannot transmit any action potential, meaning it cannot send sensory messages to the neurons.

Structure Similarities

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The structure of local anesthetics is important to its function2。Each anesthetic has a lipophilic aromatic ring that increases its lipid (fat) solubility. This increased solubility enhances its ability to reach the neurons, thereby increasing the anesthetic effects.In addition, both lidocaine and benzocaine have a terminal amine (an NH at the end)2。This portion of the structure is important in the anesthetic's ability to transform between a water-soluble form and a lipid-soluble form2。For the substance to be injected, as lidocaine often is, or to be in a suspension such as for ear drops like benzocaine often is, it needs to be water-soluble, meaning it can be in solution in water2。然而,一旦进入人体,它必须为我国orm into a lipid-soluble form so that it can penetrate the neuron and induce the anesthetic effect.

Structure Differences

Benzocaine and lidocaine also differ in their structures2。Lidocaine is an amide anesthetic because it has the amide chain (NH attached to a carbon with a double bond to oxygen)2。然而,苯坐卡因是一种酯麻醉,because it has a carbon-oxygen-carbon with a double bond to oxygen. Being an amide anesthetic, lidocaine is metabolized (or broken down) in the liver2。

Uses

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Benzocaine is often used as a topical anesthetic.It is found in many over-the-counter formulations of sunburn products, oral ulcer ointments and ear drops.Lidocaine is more potent than benzocaine and for that reason it is more often found in prescription medication2。Lidocaine may be found as a cream, gel, liquid or patch and is often used to relieve itching, burning, inflammation and pain on the skin2。Lidocaine is also often used by dentists during procedures2。

Cautions

Used in careful doses, the anesthetic effects of lidocaine and benzocaine are useful for a variety of applications; however, toxicity can occur, especially for lidocaine, because its effects penetrate deeper into the body2。If too much is used, neuron signaling can be detrimentally affected, causing the central nervous system to become depressed resulting in convulsive seizures. The U.S. Food and Drug Administration (FDA) issued a warning in January 2009 against the use of local anesthetics such as lidocaine in cosmetic purposes2。Two women who used a topical anesthetic in conjunction with laser hair removal experienced seizures that led to coma and death.