Chemical nature and properties
In its chemical structure, benzocaine is an ethyl ester of para-aminobenzoic acid. In its pure form, it is a white, completely odorless crystalline powder. When the drug comes into contact with the oral mucosa, it exhibits a mildly bitter taste and rapidly induces a characteristic sensation of numbness.
The key pharmacological feature of benzocaine that distinguishes it from most other local anesthetics is its relationship with solvents. It is extremely poorly soluble in water. Precisely because of this insolubility, it is technically impossible and inappropriate to use the drug for injection anesthesia (nerve block, infiltration anesthesia). At the same time, benzocaine is highly soluble in ethanol and various fatty oils, making it an ideal component for semi-solid and liquid dosage forms intended for surface application.
Topical application
Since benzocaine works only upon direct contact with tissues, its primary niche is topical anesthesia. The drug is applied to the skin, wounds, and ulcerated surfaces.
The main indications for skin application include various dermatological conditions accompanied by pronounced pruritus (a classic example being urticaria). Ointments, pastes, and powders are used for these purposes.
In pharmacy practice, benzocaine is frequently found in ready-made combination drugs:
- Menovazin is a popular alcohol solution for topical use.
- Amprovisol is a specialized aerosol. In addition to benzocaine, its composition includes 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 the anesthesia of mucous membranes, high-concentration oil solutions of benzocaine (from 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 administration Benzocaine is included in rectal suppositories (suppositoria). They are indicated for diseases of the rectum, such as hemorrhoids, anal fissures, and local pruritus. A well-known representative of this group is the combination drug Anestezol.
Enteral administration (oral) Although the drug is not injected, it can be taken orally. Powders, tablets, and mucosal mixtures are used for this purpose. Upon entering the digestive tract, benzocaine provides anesthesia of the gastrointestinal mucosa.
Indications for oral administration:
- Stomach pain and cramps;
- Esophageal hypersensitivity;
- Nausea and vomiting;
- Motion sickness and seasickness.
In gastroenterology, benzocaine is frequently prescribed as part of the combination tablet Bellastesin.
Briefly: answers to topical questions
In which dermatological pathologies is topical benzocaine indicated?
Topical application of benzocaine is indicated for skin conditions 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 as an impurity in illicitly prepared formulations. Such impurities cause acute poisoning, for which the following are noted:
- Hemolysis.
- Methemoglobinemia.
- Renal failure.
No other specific side effects of benzocaine preparations are indicated in the cited sources.
With which antimicrobial agents does benzocaine exhibit competitive antagonism?
Benzocaine exhibits chemical antagonism with antimicrobials from the sulfonamide group. Mechanism of interaction:
- benzocaine belongs to local anesthetics, which are derivatives of para-aminobenzoic acid (PABA) esters;
- upon hydrolysis, it releases PABA;
- PABA competes with sulfonamides and neutralizes their action.
Benzocaine is afraid of water — injections are ruled out. It only works where it can be smeared, sprinkled, or swallowed.
Class and exam questions
Why is benzocaine not used for injection 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 injection from it.
What is Amprovisol aerosol used for?
This combination drug containing benzocaine, vitamin D2, menthol, and propolis is used for local anesthesia in first- and second-degree thermal and sunburns.
Can benzocaine be taken orally?
Yes, it is used enterally (in the form of powders, mixtures, and tablets, such as Bellastesin) to anesthetize the GI mucosa in case of stomach cramps, vomiting, and motion sickness.
What else to study on this topic
- Composition and pharmacodynamics of Amprovisol aerosol components
- Comparison of benzocaine with other para-aminobenzoic acid esters
- Mechanism of action of benzocaine in motion sickness and seasickness
- Pharmacological profile of Menovazin and Bellastesin combination drugs
Master the entire topic in the «Pharmacology» course
This is a summary. The course covers everything tested in classes and exams.
- Complete study guide on "Benzocaine" and 5,304 more pages of the subject
- Assignments and quizzes after every topic — just like in a colloquium
- AI tutor answers questions on the topic anytime
- 116 video lessons on the subject
Other topics in the "Analgesics" section
Free video lessons: pharmacologyShort lessons with study notes — no registration required.
Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.