Pharmacology · Class
Local anesthetics !
Drugs that block nerve sodium channels and numb an area without loss of consciousness: stitches, dentistry, nerve blocks and spinal anesthesia.
Updated 2026-11-01
What they are
They reversibly block nerve conduction where they are applied. By their intermediate link they split into amides (lidocaine, bupivacaine) and esters (procaine, benzocaine).
Mechanism of action
They are weak bases: the uncharged form crosses the axon membrane and, once inside, the charged form blocks the pore of the voltage-gated sodium channel from the inner side. They bind best to open or inactivated channels, so they block fibers that fire often more strongly. Without sodium entry no action potential is generated and the pain signal never reaches the brain.
Target: Voltage-gated sodium channels (Nav)
Drugs in this class
- LidocaineThe most used local anesthetic: it numbs skin and nerves by blocking sodium channels. It is also a class Ib…Voltage-gated sodium channel (Nav; in the heart, Nav1.5)
- BupivacaineLong-acting amide local anaesthetic for epidurals, spinals and nerve blocks. It is the most cardiotoxic of its group.Voltage-gated sodium channels (Nav)
- RopivacaineLong-acting amide local anaesthetic, related to bupivacaine but less cardiotoxic. Used for epidurals, nerve blocks and…Voltage-gated sodium channels (Nav)
- TetracainePotent, long-acting ester local anaesthetic: eye drops for ocular procedures and an option for spinal anaesthesia.Voltage-gated sodium channels (Nav)
- CocaineThe only local anaesthetic that constricts vessels: a nasal solution for nose surgery. It raises blood pressure, can…Monoamine transporters (dopamine and noradrenaline transporters) and sodium channels
- BenzocaineTopical ester local anaesthetic in gels, sprays and lozenges for the mouth and throat. It can cause methaemoglobinaemia.Voltage-gated sodium channels (Nav)
- ProcaineThe classic ester local anaesthetic: low potency and short-acting. Today it is used mainly as part of procaine…Voltage-gated sodium channels (Nav)
Others in the class
- bupivacaine
- ropivacaine
- mepivacaine
- prilocaine
- procaine
- tetracaine
- benzocaine
Test yourself
Think of the answer, then tap the question to see it.
Why does a local anesthetic work poorly in an abscess?
The acidic pH raises the ionized fraction of the drug outside the nerve; that charged form crosses the axon membrane poorly, so less reaches its site of action.
Which drug is used for severe local anesthetic systemic toxicity?
Intravenous lipid emulsion, alongside airway support, seizure control and resuscitation.
Why is true allergy more common with ester-type local anesthetics?
Their hydrolysis by plasma cholinesterase produces para-aminobenzoic acid (PABA), a known allergen.
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: Anesthesia: MedlinePlus (MedlinePlus (U.S. National Library of Medicine), 2025); Lidocaine Transdermal Patch: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2026); eEML - Electronic Essential Medicines List (World Health Organization, 2025).
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Representative model, for educational purposes only.