Lidocaine Injection

Lidocaine injection is a widely used local anesthetic and antiarrhythmic agent. It’s available as preservative-free or with epinephrine in various concentrations and is given by multiple parenteral routes depending on the clinical purpose.

Forms & concentrations

• Solutions for injection (common concentrations): 0.5%, 1%, 2% (w/v).

• May be supplied with epinephrine (e.g., 1:100,000) to prolong effect and reduce systemic absorption.

• Sterile ampoules or vials for subcutaneous (SC), intradermal, infiltration, nerve block, epidural, or intravenous use.

• IV formulations (for antiarrhythmic use) are preservative-free and intended for bolus/infusion.

Mechanism of action

• Blocks voltage-gated sodium channels in neuronal and cardiac cell membranes.

• In peripheral nerves → prevents initiation/propagation of nerve impulses → local anesthesia.

• In myocardium → reduces automaticity and conduction velocity, suppressing ventricular arrhythmias (when given IV).

Common indications

• Local/regional anesthesia: infiltration, peripheral nerve blocks, digital blocks, dental procedures, minor surgical procedures.

• Epidural or spinal (when formulated appropriately) in some settings.

• Antiarrhythmic (IV): acute treatment of ventricular tachycardia, ventricular ectopy, and in cardiac resuscitation in select protocols.

• Topical mucosal anesthesia (when formulated for that use).

Typical dosing (general ranges — always follow local protocol)

• Local infiltration: depends on site and concentration; total dose usually limited by weight-based max.

• Peripheral nerve block: volumes and concentrations vary by block type and provider preference.

• With epinephrine permits larger total dose due to decreased systemic absorption.

• IV antiarrhythmic (adult): a typical bolus ~1–1.5 mg/kg IV over 2–3 minutes, followed (if needed) by infusion (e.g., 1–4 mg/min) — use institution protocols.

• Maximum total dose (approximate): without epinephrine often quoted ~3–5 mg/kg (lean body weight) and with epinephrine up to ~7 mg/kg — exact limits depend on formulation, route, and patient factors.

Important: dosing must be individualized (age, weight, comorbidities, concurrent drugs). Use institutional guidelines or product labeling.

Onset and duration

• Onset: rapid — minutes (depends on route and concentration).

• Duration: short to intermediate; adding epinephrine prolongs effect (can double/triple duration depending on site).

Adverse effects

Local/systemic toxicity (if absorbed systemically or overdose):

• Early CNS signs: circumoral numbness, metallic taste, tinnitus, visual disturbances, lightheadedness, agitation.

• Progressive CNS toxicity: tremor, seizures, respiratory depression, coma.

• Cardiovascular: hypotension, bradycardia, conduction block, arrhythmias, cardiovascular collapse (severe overdose).

Local reactions:

• Pain or irritation at injection site, hematoma, infection (rare).

• Transient nerve injury or prolonged numbness (rare).

Allergic reactions:

• True IgE-mediated allergy to amide local anesthetics (lidocaine) is rare; more commonly related to preservatives or metabolite sensitivity.

Contraindications & cautions

• Known hypersensitivity to lidocaine or other amide-type local anesthetics.

• Use caution (or avoid large doses) in severe hepatic impairment (metabolism reduced), severe cardiac conduction abnormalities (unless used/monitored for antiarrhythmic purpose), and in patients on certain antiarrhythmics or drugs that alter lidocaine clearance.

• Avoid high-volume blocks in end-artery areas (digital blocks with epinephrine are generally avoided in some practices).

• Pregnancy/lactation: use only if clearly needed and benefits outweigh risks — obstetric use requires careful consideration.

Drug interactions

• Drugs that inhibit hepatic metabolism (e.g., certain CYP inhibitors) can raise lidocaine levels.

• Concomitant antiarrhythmics or other local anesthetics can have additive cardiac/CNS toxicity.

• Beta-blockers, cimetidine, and others may reduce clearance — monitor dose.

Monitoring & management of toxicity

• Monitor for early CNS symptoms after large or vascular injections.

• For suspected systemic local anesthetic toxicity: stop dosing, support airway/ventilation, treat seizures (benzodiazepines preferred), provide circulatory support (fluids/vasopressors) and follow ACLS as needed.

• Lipid emulsion therapy (20% intralipid) is an established treatment for severe local anesthetic systemic toxicity (LAST) — give early in cardiovascular collapse per guidelines/protocols.

Special populations

• Elderly and hepatic impairment: reduce dose and monitor closely.

• Pediatrics: weight-based dosing essential; younger children have different pharmacokinetics.

• Pregnancy: increased cardiac output and altered protein binding may affect plasma levels.

Storage & handling

• Store according to product labeling (generally at controlled room temperature and protected from light).

• Use aseptic technique; discard single-use ampoules after use.

• Check concentration and presence/absence of epinephrine before administration.