Lidocaine

IV lidocaine is a sodium-channel-blocking class Ib antiarrhythmic used for ventricular arrhythmias (e.g., VF/pulseless VT when amiodarone is unavailable, stable monomorphic VT, PVC suppression in selected settings) and occasionally for ventricular ectopy/VT in ischemia.

• Onset (IV): Within 30–60 seconds, with peak effect in minutes
• Duration: 10–20 minutes after a bolus unless followed by a continuous infusion
• Typical adult antiarrhythmic bolus: 1–1.5 mg/kg IV (often 100 mg in a 70–100 kg adult), followed by additional boluses of 0.5–0.75 mg/kg IV every 5–10 minutes as needed, not to exceed a total of 3 mg/kg
• Maintenance infusion: 1–4 mg/min IV (≈20–50 mcg/kg/min), adjusted for age, hepatic function, and hemodynamics
• Local anesthetic uses: Infiltration, nerve blocks, and topical anesthesia. Typical maximum dose: 4.5 mg/kg (without epinephrine) and up to 7 mg/kg (with epinephrine)
• Major issues: CNS toxicity (tinnitus, perioral numbness, metallic taste, agitation, seizures) and cardiovascular toxicity (hypotension, bradycardia, QRS widening, ventricular arrhythmias, cardiac arrest) at high plasma levels
• Metabolism: Hepatically cleared (high extraction); accumulation and toxicity are more likely in liver disease, low cardiac output states, and the elderly

• Generic Name: Lidocaine hydrochloride
• Brand Names: Xylocaine, various generics

Class Ib antiarrhythmic (IV); amide local anesthetic (infiltration, nerve block, topical)

Mechanism of Action:

• Class Ib antiarrhythmic: blocks fast voltage-gated sodium channels in the His–Purkinje system and ventricular myocardium, predominantly in the inactivated state, with rapid association/dissociation kinetics
• Shortens the action potential duration and effective refractory period in ventricular tissue, particularly in ischemic or depolarized myocardium, while having relatively little effect on atrial tissue or normal Purkinje fibers
• Local anesthetic: stabilizes neuronal membranes by blocking sodium channels in peripheral nerves, inhibiting initiation and conduction of nerve impulses, thereby providing reversible loss of sensation
• Use-dependence: greater sodium-channel blockade at faster heart rates and in depolarized tissue, which is useful in ischemic ventricular arrhythmias but makes it less effective for supraventricular arrhythmias

Pharmacokinetics:

• Onset (IV): 30–60 seconds with rapid distribution to the heart and CNS
• Distribution half-life: ~8–30 minutes; large volume of distribution due to high tissue uptake and lipophilicity
• Metabolism: Extensive hepatic metabolism via CYP1A2 and CYP3A4 to monoethylglycinexylidide (MEGX) and glycinexylidide (GX), which have some antiarrhythmic and neurotoxic activity
• Elimination: Primarily renal excretion of metabolites; elimination half-life ~1.5–2 hours in healthy adults but prolonged in hepatic dysfunction, low cardiac output states, or CHF (can reach 3–5 hours or more)
• High hepatic extraction ratio: Clearance is flow limited; decreased hepatic blood flow (shock, HF) leads to higher plasma levels for a given infusion rate
• Protein binding: ~60–80%, primarily to alpha-1 acid glycoprotein; levels may be altered in critical illness

• Alternative or adjunct in ventricular fibrillation or pulseless VT during cardiac arrest when amiodarone is unavailable or ineffective
• Treatment of stable monomorphic VT (with a pulse) when amiodarone is unavailable or contraindicated, in consultation with cardiology
• Suppression of ventricular ectopy or nonsustained VT in ischemia or post-MI in selected patients (usage has decreased as routine prophylaxis is not beneficial)
• Adjunct for painful ventricular arrhythmias (e.g., "VT storm") when combined with sedation and other antiarrhythmics in specialized care
• Local anesthetic indications (infiltration, nerve block, topical) for procedures in ED/ICU

Available Forms:

• IV antiarrhythmic solution: typically 100 mg/5 mL (20 mg/mL) vials or prefilled syringes; 1% solution = 10 mg/mL; 2% solution = 20 mg/mL
• Premixed infusion bags: e.g., 1 g in 250 mL (4 mg/mL) or 2 g in 500 mL for lidocaine drips
• Local anesthetic formulations: 0.5%, 1%, and 2% solutions (with or without epinephrine) for infiltration or nerve block; topical gels, viscous solutions, and patches for mucosal or dermal anesthesia

Adult IV Antiarrhythmic Dosing (Always follow ACLS/local protocol):

Contraindications:

• Known hypersensitivity to lidocaine or other amide-type local anesthetics
• Complete heart block without a functioning pacemaker (risk of asystole)
• Severe sinoatrial, AV, or intraventricular block in the absence of pacing support (for IV antiarrhythmic use)
• Wolff–Parkinson–White or other accessory pathways when treating supraventricular arrhythmias (lidocaine is not indicated for SVT)

Major Precautions:

• Hepatic impairment, congestive heart failure, and shock: reduced clearance and increased risk of toxicity; reduce infusion rate and cumulative dosing
• Elderly and low body-weight patients: more susceptible to CNS toxicity; use lower doses
• Seizure disorders: lidocaine can lower seizure threshold at high levels
• Concurrent use of other antiarrhythmics or sodium-channel–blocking agents (e.g., class I agents, tricyclics): additive cardiac depressant and pro-arrhythmic effects
• Local anesthetic use in highly vascular areas: increased systemic absorption and toxicity risk; aspirate before injection and calculate total dose carefully

Common (therapeutic range or mild toxicity):

• Perioral numbness, tongue paresthesia
• Tinnitus, metallic taste
• Lightheadedness, dizziness, blurred vision
• Nausea, vomiting, mild confusion

Serious (dose-related toxicity):

• Seizures and status epilepticus
• Severe CNS depression, coma, respiratory arrest
• Hypotension, bradycardia, AV block, asystole
• Ventricular arrhythmias, widened QRS, cardiac arrest
• Local anesthetic systemic toxicity (LAST) with high-dose local/regional use: cardiovascular collapse requiring lipid emulsion therapy

Hepatic Impairment:

• Reduce bolus doses and maintenance infusion rates significantly
• Monitor closely for signs of toxicity (CNS symptoms, cardiac effects)
• Consider lower maximum cumulative dose

Heart Failure / Low Cardiac Output:

• Reduced hepatic blood flow decreases clearance
• Use lower doses and slower infusion rates
• Increased risk of accumulation and toxicity

Elderly Patients:

• More susceptible to CNS and cardiac toxicity
• Start with lower bolus doses (0.5–0.75 mg/kg)
• Reduce maintenance infusion rates

Pregnancy & Lactation:

• Crosses the placenta; use with caution during pregnancy
• Generally considered compatible with breastfeeding at therapeutic doses
• Local anesthetic use is common during labor and delivery

Clinical Monitoring:

• Continuous ECG monitoring for QRS duration, QT interval, heart rate, and rhythm
• Frequent blood pressure and hemodynamic assessment, especially with bolus/infusion in unstable patients
• Neurologic status: early CNS symptoms (tinnitus, perioral numbness, confusion) as warning signs of toxicity
• Liver function and signs of heart failure in patients on prolonged infusions

Laboratory Monitoring:

• Serum lidocaine levels in prolonged infusions or high-risk patients, where available (therapeutic antiarrhythmic range typically ~1.5–5 mcg/mL)

• 1. Lexicomp. (2025). Lidocaine (systemic): Drug information. Wolters Kluwer.
• 2. American Heart Association. (2020). 2020 AHA Guidelines for CPR and ECC.
• 3. Drugs.com. (2024). Lidocaine hydrochloride injection: Dosage and administration. https://www.drugs.com/dosage/lidocaine.html
• 4. EMCrit Project. (2023). Ventricular arrhythmias (IBCC). https://emcrit.org/ibcc/vtach/
• 5. LITFL. (2023). Lidocaine toxicity. https://litfl.com/lidocaine-toxicity/