Lidocaine is a widely used amide-type local anesthetic and Class Ib antiarrhythmic agent. In the Indian market, the 20mg strength is most commonly available as a topical gel, cream, or spray for localized pain relief and as a component of injectable solutions for minor surgical procedures, nerve blocks, and dental anesthesia. It functions by blocking voltage-gated sodium channels, thereby inhibiting the initiation and conduction of nerve impulses, leading to reversible loss of sensation.
Adult: TOPICAL (2% Gel/Cream/Spray): Apply a thin layer to affected area up to 3-4 times daily. Maximum: Do not exceed 20g of 2% gel (400mg lidocaine) per day. INJECTABLE (Infiltration/Nerve Block): Dose varies by procedure. Maximum single dose: 4.5 mg/kg (not to exceed 300mg) without epinephrine. With epinephrine: 7 mg/kg (not to exceed 500mg). Always use the lowest effective dose.
Note: TOPICAL: Apply only to intact skin or mucous membranes as directed. Do not apply to large areas or under occlusive dressings for prolonged periods. INJECTABLE: Use aseptic technique. Aspirate before injection to avoid intravascular administration. Use appropriate concentration and volume for the intended block. For IV antiarrhythmic use, requires cardiac monitoring.
Lidocaine stabilizes neuronal membranes by reversibly binding to and inhibiting voltage-gated sodium channels in the axonal membrane. This binding is use-dependent (preferentially binds to open/inactivated channels). The inhibition prevents sodium ion influx, thereby blocking the depolarization phase of the action potential. This halts the initiation and propagation of electrical impulses, resulting in a reversible loss of sensation (anesthesia) in a localized area.
Pregnancy: Category B (US FDA). No well-controlled studies in pregnant women. Use only if clearly needed, especially during first trimester. Crosses the placenta. Fetal bradycardia may occur. Considered relatively safe for local anesthesia during labor (e.g., perineal infiltration).
Driving: May cause dizziness, drowsiness, or blurred vision. Patients should be advised not to drive or operate machinery until the effects (especially numbness if affecting motor function) have worn off.
| Beta-blockers (e.g., Propranolol) | Reduce hepatic blood flow, decreasing lidocaine metabolism, increasing risk of toxicity. | Major |
| Cimetidine | Inhibits CYP enzymes, reduces lidocaine clearance, increases plasma levels and toxicity risk. | Major |
| Class I & III Antiarrhythmics (e.g., Amiodarone, Flecainide) | Additive cardiac depressant effects, increased risk of arrhythmias and heart block. | Major |
| CYP3A4 Inhibitors (e.g., Ketoconazole, Erythromycin) | Increase lidocaine plasma concentrations. | Moderate |
| CYP1A2 Inducers (e.g., Smoking, Omeprazole) | May decrease lidocaine plasma concentrations. | Moderate |
| Succinylcholine | Lidocaine may prolong neuromuscular blockade. | Moderate |
| Vasoconstrictors (e.g., Epinephrine) | Prolong duration of action and reduce systemic absorption when co-administered locally. | Minor (Beneficial) |
Same composition (Lidocaine (20mg)), different brands: