Ingredients --

Benzocaine

Chemical Formula:

Benzocaine

Synonyms

Ethyl p-aminobenzoate
Ethyl PABA
Anesthesin

Description

White crystalline powder.

Uses

Benzocaine is a topical anesthetic. It numbs wherever it is applied. It is widely used in first aid creams and sunburn remedies.

Chemistry lesson

Benzocaine is an ester, a compound made from the organic acid PABA (para amino benzoic acid) and the alcohol ethanol.

Para amino benzoic acid

Other esters of PABA have similar anesthetic properties.

Procaine (novocaine)

Dentists use procaine (also called novocaine) to numb teeth and gums before dental work.

Lidocaine (xylocaine)

Another topical anesthetic, similar to benzocaine, is lidocaine, which is used to relive the pain of shingles (herpes zoster) infections. Lidocaine is called an amide anesthetic, because it is not an ester (the alcohol is replaced by an amide, the nitrogen group). Amide anesthetics are metabolized by the liver, and are less prone to cause allergic reactions. If an anesthetic has an "i" in the prefix (lidocaine, prilocaine, bupivicaine) it is an amide anesthetic.

Denatonium benzoate

A small change to lidocaine (adding a benzyl group) makes the molecule denatonium benzoate, the bitterest tasting substance known. It is used to denature alcohol, (Specially Denatured alcohol 40, or SD-40, is ethanol denatured (made unfit for drinking) by a tiny amount denatonium benzoate).

Cocaine hydrochloride

You can see a resemblance between benzocaine, procaine, and the compound that gave Coca Cola its first name. Cocaine also has a numbing effect, in addition to its effects as an addictive central nervous system stimulant.

Some other anesthetics with similar structures are prilocaine, tetracaine, ropivacaine, bupivacaine, chloroprocaine, and mepivacaine:

Prilocaine