Lidocaine

Lidocaine, also known as lignocaine, is an amide-type local anesthetic and antiarrhythmic drug. It exerts its effect by reversibly blocking voltage-gated sodium channels in nerve membranes, inhibiting action potential initiation and propagation. In cardiac tissue, this blockade reduces automaticity and slows conduction, making it useful for certain arrhythmias when given intravenously.

Medical uses include local anesthesia for minor procedures (infiltration, nerve blocks), regional anesthesia (epidural or spinal), dental anesthesia, and topical analgesia for mucosal surfaces. It is often formulated with epinephrine to reduce systemic absorption and prolong effect, with caution in end-artery areas.

Formulations include injectable lidocaine hydrochloride solutions (various concentrations) and topical preparations (gels, creams, sprays).

Pharmacokinetics: lidocaine is an amide-type local anesthetic that is hepatically metabolized via cytochrome P450 enzymes to active and inactive metabolites. The elimination half-life is about 1.5 to 2 hours, and is prolonged in hepatic impairment. Onset is rapid (roughly 1–5 minutes for infiltration, 5–10 minutes for nerve blocks) and duration depends on dose, site, and use of vasoconstrictors; epinephrine can extend duration.

Safety and contraindications: contraindicated in hypersensitivity to amide local anesthetics. Caution is warranted in severe hepatic disease, congestive heart failure, hypotension, conduction abnormalities, and in the elderly. Systemic toxicity can manifest as central nervous system symptoms (dizziness, tinnitus, seizures) and cardiovascular effects (bradycardia, hypotension, arrhythmias). Interactions exist with other central nervous system depressants and antiarrhythmics; avoid use around end-artery sites when using epinephrine.

History: lidocaine was introduced in the 1940s and became the first widely used amide local anesthetic. Brand names include Xylocaine and lignocaine.