Pharmacology · Local anesthetics
Procaine !
The classic ester local anaesthetic: low potency and short-acting. Today it is used mainly as part of procaine benzylpenicillin.
Updated 2026-11-01
Mechanism of action
Procaine, the prototype ester local anaesthetic, blocks voltage-gated sodium channels and stops nerve conduction. Plasma esterases hydrolyse it rapidly, so its action is short, and one of its products is para-aminobenzoic acid (PABA), responsible for ester allergies. Combined with benzylpenicillin it forms a poorly soluble salt that releases the antibiotic slowly from muscle.
- Blocks the nerve sodium channel
- Short-lasting anaesthesia
- Plasma cholinesterase hydrolyses it to PABA
- PABA explains ester allergy
Pharmacokinetics
- Metabolism
- Rapid hydrolysis by plasma esterases to para-aminobenzoic acid.
- Elimination
- Kidney, as metabolites.
Indications
- Component of intramuscular procaine benzylpenicillin, whose slow release prolongs the antibiotic's effect
Adverse effects
Common
- Allergic skin reactions
- Dizziness and perioral numbness if much is absorbed
Contraindications
- Allergy to procaine, PABA or other ester-type anaesthetics
Key interactions
- Other esters (tetracaine, benzocaine)
- Cross-allergy through a common metabolite.
- Neuromuscular blockers
- Procaine can enhance block at the motor end plate.
What is monitored
- Signs of allergy after injection
- Neurological signs of toxicity if accidentally injected into a vessel
Administration and safety
- Procaine benzylpenicillin is an intramuscular formulation: confirm the route before injecting.
- Ask first about allergy to penicillin and to ester-type anaesthetics.
Nursing care
- Before: allergies to penicillin, procaine and other «-caines».
- After: observe the patient for a while in case allergic reactions or neurological symptoms appear.
Test yourself
Think of the answer, then tap the question to see it.
Why is the action of procaine short?
Plasma esterases hydrolyse it rapidly.
Which procaine metabolite explains allergies to ester anaesthetics?
Para-aminobenzoic acid (PABA).
In which medicine is procaine most often found today?
In procaine benzylpenicillin, a slow-release salt for intramuscular injection.
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: 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.