Benzocaine
[CAS# 94-09-7]

Identification

• Classification: API >> Anesthetic agents >> Local anesthetics
• Name: Benzocaine
• Synonyms: Benzocaine BP98; Anesthesin; Parathesin; Auralgan Otic; Ethyl aminobenzoate; Ethyl 4-aminobenzoate
• Molecular Formula: C₉H₁₁NO₂
• Molecular Weight: 165.19
• CAS Registry Number: 94-09-7
• EC Number: 202-303-5
• SMILES: CCOC(=O)C1=CC=C(C=C1)N

Properties

• Density: 1.17
• Melting point: 89-92 ºC
• Boiling point: 172 ºC (17 torr)

Safety Data

• Hazard Symbols: GHS07;GHS08 Danger
• Hazard Statements: H317-H370
• Precautionary Statements: P260-P261-P264-P270-P272-P280-P302+P352-P308+P316-P321-P333+P317-P362+P364-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Skin sensitization	Skin Sens.	1	H317
Specific target organ toxicity - single exposure	STOT SE	1	H370
Skin irritation	Skin Irrit.	2	H315
Eye irritation	Eye Irrit.	2	H319
Specific target organ toxicity - single exposure	STOT SE	3	H335
Acute toxicity	Acute Tox.	4	H332
Chronic hazardous to the aquatic environment	Aquatic Chronic	2	H411
Acute toxicity	Acute Tox.	4	H312
Eye irritation	Eye Irrit.	2A	H319
Chronic hazardous to the aquatic environment	Aquatic Chronic	4	H413

Discovory and Applicatios

The development of benzocaine dates back to the late 19th and early 20th centuries, when the search for safer and more effective local anesthetics was underway. The first generation of local anesthetics, cocaine, had significant drawbacks, including high addictiveness and systemic toxicity. This prompted chemists to search for alternatives that retained the anesthetic properties without the associated risks.

Benzocaine was synthesized in 1890 by German chemist Eduard Ritsert, who sought to create a safer alternative to cocaine. Originally known as "anestheticin," benzocaine was developed from para-aminobenzoic acid (PABA). Its success as a local anesthetic stemmed from its ability to block sodium channels on nerve endings, thereby preventing pain signal transmission. Compared to its precursor, benzocaine was much safer and was soon used for a variety of medical purposes.

Benzocaine (C9H11NO2) is an ester of para-aminobenzoic acid, characterized by a benzene ring attached to the ester and amino groups. It is a white crystalline powder that is virtually insoluble in water, but soluble in alcohol, ether, and chloroform. Benzocaine's lipophilic nature allows it to effectively penetrate biological membranes to numb specific areas of the skin or mucous membranes.

Benzocaine is primarily used as a local anesthetic to relieve pain and itching. It is a key ingredient in a variety of over-the-counter pharmaceutical products, including pain-relieving sprays, gels, ointments, and lozenges. Its ability to effectively numb the skin and mucous membranes makes it valuable in treating conditions such as sunburn, insect bites, sore throats, and minor cuts.

In dentistry, benzocaine is often used to numb the gums before injections, to relieve the pain of mouth ulcers, and to temporarily relieve toothaches. Benzocaine's rapid onset and ease of use make it a practical choice for patients and dental professionals to provide pain relief without the systemic effects of injected anesthetics.

Benzocaine is used in minor surgeries and diagnostic exams, such as endoscopy or cystoscopy, that require local anesthesia to reduce discomfort. It relieves local pain, making the procedure less invasive and more comfortable.

In otolaryngology, benzocaine is used to numb the ear or nasal cavity before an exam or minor surgery. It helps relieve discomfort during procedures such as earwax removal or nasal endoscopy.

Benzocaine is a common ingredient in over-the-counter oral pain relief products, including gels and lozenges. These products are used to relieve pain from mouth sores, sore throats, and minor oral irritations. The anesthetic properties quickly relieve discomfort and promote healing.

Hemorrhoid creams and ointments contain benzocaine to relieve pain and itching from hemorrhoids. Its local anesthetic properties help reduce symptoms and increase patient comfort.

Over-the-counter creams and sprays containing benzocaine can be used to relieve itching and pain from skin irritations, including rashes, insect bites, and sunburns. It numbs the affected area, relieves symptoms, and helps reduce the urge to scratch or rub irritated skin.

While benzocaine is generally safe for topical use, in rare cases it can cause methemoglobinemia, a serious condition in which hemoglobin cannot effectively release oxygen to body tissues. This risk is particularly evident with high concentrations or long-term use, so caution should be used when using the product on infants or people with susceptible medical conditions. Benzocaine can also cause allergic reactions in some people. Symptoms may include itching, redness, and swelling at the application site. Always use benzocaine products as directed and consult a doctor if adverse reactions occur.

Benzocaine is used in the pharmaceutical industry as an intermediate in the synthesis of other local anesthetics. Its role in drug formulation has helped create a variety of anesthetic products that have contributed to advances in pain management.

In research and laboratory settings, benzocaine is used as a chemical synthesis reagent and in the formulation of experimental anesthetic compounds. Its effectiveness and reliability make it a valuable tool in scientific research.

References

1979. Comparative study of the action of procaine and benzocaine on normal and aconitine-modified sodium channels. Tsitologiia, 21(6).
URL: https://pubmed.ncbi.nlm.nih.gov/462546

2010. Is threshold for treatment of methemoglobinemia the same for all? A case report and literature review. The American Journal of Emergency Medicine, 28(6).
DOI: 10.1016/j.ajem.2009.10.014

2000. Methemoglobinemia related to topical benzocaine use: Is it time to reconsider the empiric use of topical anesthesia before sedated EGD? Gastrointestinal Endoscopy, 52(5).
DOI: 10.1067/mge.2000.110078