Benzocaine

Benzocainum

For medical students2 min readUpdated 2026-10-10

Benzocaine is a local anesthetic used exclusively for surface anesthesia. The main feature of the drug lies in its physicochemical properties, which completely preclude injection and determine its choice of dosage forms.

Chemical natureEthyl ester of p-aminobenzoic acid

SolubilityPoorly soluble in water, highly soluble in alcohol and fatty oils

Local effectCauses tongue numbness upon contact with mucous membranes, has a mildly bitter taste

Dosage formsOintments, pastes, powders, suppositories, tablets, mucilaginous mixtures

Chemical Nature and Properties

Chemically, benzocaine is the ethyl ester of para-aminobenzoic acid. In its pure form, it is an odorless white crystalline powder. When applied to the oral mucosa, it exhibits a mildly bitter taste and rapidly induces a characteristic numbness.

A key pharmacological feature of benzocaine, distinguishing it from most other local anesthetics, is its solubility profile. It is extremely poorly soluble in water. Because of this insolubility, it is technically impossible and inappropriate to use the drug for injectable anesthesia (nerve blocks, infiltration anesthesia). However, benzocaine is highly soluble in ethanol and various fatty oils, making it an ideal component for soft and liquid dosage forms designed for surface application.

Topical Application

Because benzocaine works only upon direct contact with tissues, its primary niche is surface anesthesia. The drug is applied to the skin, wounds, and ulcerated surfaces.

Main indications for cutaneous application include various dermatological conditions accompanied by pronounced pruritus (urticaria being a classic example). Ointments, pastes, and powders are used for these purposes.

In pharmacy practice, benzocaine is often found in ready-made combination products:

Menovazin — a popular alcohol-based topical solution.
Amprovisol — a specialized aerosol containing benzocaine, menthol, vitamin $D_2$ (ergocalciferol), glycerin, propolis, and ethanol. This combination is intended for local anesthesia and the treatment of first- and second-degree thermal and sunburns.

For mucosal anesthesia, high-concentration oil solutions of benzocaine (5% to 20%) are typically used.

Application in Proctology and Gastroenterology

The action of benzocaine is not limited to the skin and external mucous membranes. It is actively used to relieve pain and discomfort in internal organs accessible to surface contact with the drug.

Rectal Application Benzocaine is included in rectal suppositories indicated for rectal disorders such as hemorrhoids, anal fissures, and local pruritus. A well-known representative of this group is the combination product Anestezol.

Enteral Application (Oral) Although the drug is not injected, it can be taken orally in the form of powders, tablets, and mucilaginous mixtures. Upon reaching the digestive tract, benzocaine anesthetizes the mucosa of the gastrointestinal tract.

Indications for oral administration:

Stomach pain and spasms;
Esophageal hypersensitivity;
Nausea and vomiting;
Motion sickness (travel sickness).

In gastroenterology, benzocaine is frequently prescribed as part of combination tablets such as Bellastesin.

Mnemonic

Benzocaine fears water — injections are ruled out. It only works where you can smear it, sprinkle it, or swallow it.

Frequently asked questions

In which dermatological pathologies is topical benzocaine indicated?

Topical application of benzocaine is indicated for skin diseases accompanied by pruritus. Indications include:

Urticaria.
First- and second-degree sunburns and thermal burns — local anesthesia as part of the Amprovisol combination aerosol.

Benzocaine preparations are also used to anesthetize wound and ulcer surfaces.

What side effects are characteristic of benzocaine preparations?

Sources describe toxic effects associated with benzocaine when used as an adulterant in illicit or crude preparations. Such exposures cause acute poisonings, characterized by:

Hemolysis.
Methemoglobinemia.
Renal failure.

No other specific side effects of standard benzocaine medications are listed in the referenced sources.

With which antimicrobial agents does benzocaine exhibit competitive antagonism?

Benzocaine exhibits chemical antagonism with antimicrobial agents from the sulfonamide group. Mechanism of interaction:

benzocaine belongs to local anesthetics that are esters of para-aminobenzoic acid (PABA);
upon hydrolysis, it releases PABA;
PABA competes with sulfonamides and neutralizes their antibacterial action.

Why is benzocaine not used for injectable anesthesia?

This is due to its physicochemical properties. Benzocaine is practically insoluble in water, making it impossible to prepare a safe and effective aqueous solution for injections.

What is the Amprovisol aerosol used for?

This combination product containing benzocaine, vitamin D2, menthol, and propolis is used for local anesthesia of first- and second-degree thermal and sunburns.

Can benzocaine be taken orally?

Yes, it is used enterally (as powders, mixtures, and tablets, such as Bellastesin) to anesthetize the GI mucosa during gastric spasms, vomiting, and motion sickness.

Go deeper

Composition and pharmacodynamics of Amprovisol aerosol components
Comparison of benzocaine with other PABA ester local anesthetics
Mechanism of action of benzocaine in motion sickness
Pharmacological profile of Menovazin and Bellastesin combination drugs