Benzocaine

Toxicity

Patients experiencing an overdose may present with local anesthetic systemic toxicity syndrome, decreased cardiovascular function, decreased central nervous system function, cardiac arrest, bradycardia, hypotension, cardiac arrhythmias, syncope, and seizures. Patients should be treated with symptomatic and supportive measures which include airway maintenance, controlling seizures, and hemodynamic stabilization.

Description

Benzocaine (ethyl p-aminobenzoate) is used topically by itself or in combination with menthol or phenol in nonprescription dosage forms such as gels, creams, ointments, lotions, aerosols, and lozenges to relieve pain or irritation caused by such conditions as sunburn, insect bites, toothache, teething, cold sores or canker sores in or around the mouth, and fever blisters. Benzocaine is a lipophilic local anesthetic agent with a short duration of action.
Like most amino ester-type local anesthetics, it is easily hydrolyzed by plasma cholinesterase. Because of its low pKa, however, it is un-ionized under most physiological conditions and, therefore, can only bind to the lipid side of the local anesthetic receptor. It also can easily cross membranes into systemic circulation to cause systemic toxicities. Furthermore, being a PABA derivative, it has similar allergenic properties to procaine and is contraindicated with sulfonamide antibacterial agents.

Description

Benzocaine, a common ingredient in sunburn remedies and first aid creams, is a topical anesthetic—it numbs the nerve endings near the surface of the skin where it is applied. This ethyl ester of?p-aminobenzoic acid (PABA, a common sunscreen ingredient) can react with compounds in sunscreens and hair dyes or produce an allergic reaction.

The Uses of Benzocaine

Benzocaine is used as an anesthetic (Local and topical) that in products such as burn and sunburn remedies, hemorrhoidal creams, suppositories, creams for treatment of poison ivy, oral and gingival products, sore-throat sprays/lozenges, astringents, appetite suppressants, callus and wart remedies, athlete's-foot remedies, toothache- and denture-irritation products.

Background

Benzocaine is an ester local anesthetic that acts by preventing transmission of impulses along nerve fibers and at nerve endings. It is commonly used for local anesthesia in many over the counter products. Benzocaine was first used for local anesthesia in dentistry.

Indications

Benzocaine is indicated for local anesthesia in dentistry, minor trauma, and as preparation for infiltrative anesthesia. Benzocaine products are indicated for topical anesthesia in a wide variety of conditions including skin irritation, oral pain, and hemorrhoids.

What are the applications of Application

Benzocaine is a surface anesthetic

Pharmacokinetics

Benzocaine is indicated for use as a topical anesthetic. It has a duration of action of approximately 10 minutes and a wide therapeutic window. Patients should be counselled regarding the risks of methemoglobinemia.

Metabolism

Benzocaine undergoes ester hydrolysis to form 4-aminobenzoic acid, acetylation to form acetylbenzocaine, or N-hydroxylation to form benzocaine hydroxide. 4-aminobenzoic acid can be acetylated or acetylbenzocaine can undergo ester hydrolysis to form 4-acetaminobenzoic acid.