Pharmacology · Local anesthetics
Benzocaine !
Topical ester local anaesthetic in gels, sprays and lozenges for the mouth and throat. It can cause methaemoglobinaemia.
Updated 2026-11-01
Mechanism of action
Benzocaine is an ester of para-aminobenzoic acid (PABA) without the terminal amino group of other local anaesthetics. It is poorly soluble in water, so it stays on the surface where it is applied, is little absorbed and gives sustained topical anaesthesia by blocking sodium channels in nerve endings.
- Applied to skin or mucosa
- Poorly soluble: stays on the surface
- Blocks sodium channels in nerve endings
- Relieves local pain temporarily
Pharmacokinetics
- Absorption
- Little absorption from skin and mucosa.
- Metabolism
- Hydrolysis by plasma esterases.
Indications
- Topical anaesthesia of mucosa (mouth, throat) and skin for minor discomfort or before procedures
Adverse effects
Common
- Local burning or stinging
- Contact dermatitis
Contraindications
- Allergy to benzocaine or other ester-type anaesthetics
Key interactions
- Other drugs that can cause methaemoglobinaemia
- Higher risk of methaemoglobinaemia.
- Other ester anaesthetics
- Cross-allergy.
What is monitored
- Colour of skin and lips, breathlessness and oximetry after use on large mucosal areas
- Signs of allergy
Administration and safety
- Use the smallest amount possible, only on the area needed and for a few days.
Nursing care
- Teach patients and families to recognise bluish skin, headache, dizziness, tiredness or shortness of breath after use, and to seek care at once.
- If bluish colour, breathlessness or tiredness appear after use: seek care at once.
- Ask about allergies to ester-type anaesthetics.
Test yourself
Think of the answer, then tap the question to see it.
Which serious blood complication can benzocaine cause?
Methaemoglobinaemia: the skin turns bluish, with headache, dizziness, tiredness and shortness of breath.
Why is benzocaine used only topically?
It is poorly soluble in water: it stays on the surface where it is applied and is little absorbed.
What chemical type of local anaesthetic is benzocaine?
An ester: it shares cross-allergy with other ester anaesthetics.
Related drugs
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Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: Methemoglobinemia: MedlinePlus Medical Encyclopedia (MedlinePlus (U.S. National Library of Medicine), 2026); Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 25 (McGraw Hill, 2023); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).
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Representative model, for educational purposes only.