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Lidocaine

*Lidocainum*

For medical students2 min readUpdated 2026-10-10

Lidocaine is a versatile amide-type local anesthetic used for all standard types of regional anesthesia. The drug is characterized by high clinical activity, a rapid onset of action, and additional pronounced antiarrhythmic properties.

Chemical StructureSubstituted amide (acetanilide derivative), highly soluble in water and alcohol.

DurationActs twice as long as procaine due to slower metabolism.

ToxicityDirectly depends on solution concentration (significantly increases at 1–2%).

Special PropertyPronounced antiarrhythmic activity; used as a standalone antiarrhythmic agent.

Chemical Nature and Pharmacological Advantages

Chemically, lidocaine is a substituted amide derived from acetanilide. It is highly soluble in both water and alcohol.

Its classification as an amide determines its metabolic profile: it is degraded in the body significantly slower than ester-type local anesthetics (e.g., procaine). This ensures a longer duration of action.

Compared to classic ester anesthetics, lidocaine offers several distinct advantages:

High potency: Its local anesthetic effect is approximately 2.5 times greater than that of procaine.
Onset speed: The analgesic effect develops much faster.
Duration: The duration of anesthesia is doubled.
Hypoallergenicity: Lidocaine is the drug of choice for patients with a diagnosed intolerance to procaine and other esters.

Indications for Use

Lidocaine is considered a universal anesthetic because it is effective for all types of local anesthesia. The specific route of administration (local or parenteral), as well as the volume and concentration of the solution, are always chosen individually based on the nature of the surgical procedure.

Main indications:

Infiltrative anesthesia: Widely used in various surgical procedures for layer-by-layer tissue infiltration.
Nerve block anesthesia: Used in dental practice, limb surgery, and major nerve plexus blocks.
Epidural and spinal anesthesia: Used for surgical interventions on the pelvic organs and lower extremities.
Topical (surface) anesthesia: Used to anesthetize mucous membranes in urology, ophthalmology, dentistry, bronchoscopy, and to relieve discomfort from burns.

Side Effects and Signs of Toxicity

The toxicity of lidocaine directly correlates with the concentration used. When using weak solutions (0.5%), the safety profile is comparable to procaine. However, increasing the concentration to 1–2% significantly raises the risk of adverse reactions.

In overdose or systemic toxicity, the following symptoms develop:

Central Nervous System: Patients may complain of headache, dizziness, tinnitus, and vision disturbances. Numbness of the tongue and oral mucosa frequently occurs. Drowsiness or, conversely, marked agitation may be observed.
Motor system: Tremor of the extremities and muscle twitching.
Cardiovascular system: Bradycardia (decreased heart rate) is characteristic.
Severe cases: Severe toxicity carries a risk of dangerous respiratory depression.

Drug Interactions

Lidocaine is frequently used in combinations to modify its effects and safety profile.

With vasoconstrictors: To prolong the anesthetic effect, epinephrine (as a 0.1% solution) is added to the lidocaine solution. This causes vasoconstriction at the injection site, which slows the absorption of the anesthetic into the systemic circulation and reduces the risk of systemic toxic reactions.
With sulfonamides: Unlike procaine, the metabolism of lidocaine does not yield para-aminobenzoic acid (PABA). Consequently, lidocaine does not impair the antimicrobial activity of sulfonamides, making their co-administration completely safe.

Mnemonic

Lidocaine is a dual-action agent: it "freezes" nerve impulses (local anesthetic) and "calms" the heart rhythm (antiarrhythmic).

Frequently asked questions

What is the mechanism of the local anesthetic action of lidocaine?

The local anesthetic mechanism of lidocaine involves the blockade of voltage-gated sodium channels. The drug prevents the influx of sodium ions, thereby inhibiting the depolarization of the cell membrane. Lidocaine belongs to the class of local anesthetics for which sodium channel blockade is the primary mechanism of action.

In which types of cardiac arrhythmias is lidocaine indicated?

Lidocaine is indicated for the treatment of various ventricular arrhythmias. The drug is used in the following conditions:

Ventricular tachycardia and ventricular extrasystoles.
Ventricular arrhythmias in the acute phase of myocardial infarction (it is a drug of choice).
Ventricular arrhythmias caused by cardiac glycoside toxicity.
Ventricular tachycardias following cardiac surgery.
Polymorphic ventricular tachycardia (Torsades de pointes) as part of combination therapy.

What are the contraindications to lidocaine administration?

Contraindications to lidocaine include severe cardiac conduction disturbances and hypersensitivity. The drug should not be used in the following conditions:

Hypersensitivity to lidocaine or other amide anesthetics (as well as additives like epinephrine or sulfites).
Sick sinus syndrome (especially in elderly patients).
Atrioventricular block.
Marked bradycardia.
Cardiogenic shock.

Where and by which enzymes is lidocaine metabolized?

Lidocaine is metabolized primarily in the liver by microsomal enzymes. As an amide local anesthetic, its biotransformation occurs via hepatic microsomal oxidation and dealkylation. Lidocaine undergoes high first-pass hepatic metabolism, meaning that a significant portion is inactivated during its initial passage through the portal circulation.

What is the maximum allowable dose of lidocaine for infiltration anesthesia?

The maximum allowable dose of lidocaine for injection, including infiltration anesthesia, is 4.4 mg/kg of body weight, not to exceed 300 mg (or 500 mg when combined with epinephrine).

Why is lidocaine frequently combined with epinephrine?

Epinephrine acts as a vasoconstrictor. Its addition slows the systemic absorption of lidocaine, which prolongs the duration of anesthesia and reduces the risk of systemic toxicity.

Can lidocaine be administered to patients taking sulfonamides?

Yes. The metabolism of lidocaine does not produce para-aminobenzoic acid (PABA), so it does not interfere with the antibacterial action of sulfonamides.

How does lidocaine toxicity depend on solution parameters?

Toxicity depends directly on concentration. A 0.5% solution is comparable in safety to procaine, whereas 1–2% solutions have significantly higher toxicity.

What is the alternative if a patient has an allergy to procaine?

In cases of procaine intolerance, lidocaine becomes the drug of choice because it belongs to a different chemical group (amides rather than esters).

Go deeper

Detailed mechanism of the antiarrhythmic action of lidocaine
Comparative analysis of amide and ester metabolism
Criteria for selecting solution concentration and volume for various types of anesthesia
Pathogenesis of seizures and respiratory depression in overdose