Lidocaine Injection

Introduction Overview

Generic Name

lidocaine injection

Brand Name

Xylocaine-MPF

Dosage Form

injectable solution

Drug Class

Group I antiarrhythmics, Local injectable anesthetics

Pharmacokinetics

Absorption:
Lidocaine administered as Xylocaine-MPF is typically delivered via injection either intravenously, subcutaneously, or intramuscularly depending on the indication. When used as a local anesthetic, it is injected directly to the target tissue where absorption into systemic circulation is gradual and variable depending upon the vascularity of the site. Higher vascularity leads to more rapid systemic absorption. When administered intravenously for antiarrhythmic effects, absorption is immediate as it enters systemic circulation directly. Absorption from epidural spaces is slower and influenced by local tissue characteristics.

Distribution:
Once absorbed, lidocaine exhibits widespread distribution throughout body tissues, with a large volume of distribution estimated to be approximately 1.3-2.1 L/kg. It crosses biological membranes easily due to its moderate lipophilicity and protein binding (~60-80%) primarily to alpha-1 acid glycoprotein in plasma. Lidocaine distributes to highly perfused organs including the heart, liver, lungs, kidneys, and brain. The drug crosses the blood-brain barrier and placental barrier. Distribution correlates clinically with both therapeutic and toxic effects, particularly in the central nervous and cardiovascular systems.

Metabolism:
Lidocaine undergoes extensive hepatic metabolism primarily via cytochrome P450 enzymes CYP1A2 and CYP3A4. The metabolic process includes oxidative deethylation to its major active metabolite monoethylglycinexylidide (MEGX), which has similar but less potent pharmacologic activity, followed by further metabolism to glycinexylidide and then hydrophilic metabolites. Metabolism is subject to variability influenced by hepatic function, enzyme inhibitors, or inducers. Impaired hepatic function significantly prolongs lidocaine clearance.

Elimination:
Lidocaine and its metabolites are primarily excreted by the kidneys. The elimination half-life averages 1.5 to 2 hours in healthy adults but can be prolonged in patients with liver impairment or congestive heart failure. Approximately 90% of the administered dose is excreted renally, mostly as metabolites. The unchanged drug accounts for a minor percentage of renal excretion. Renal impairment may reduce clearance of metabolites but has lesser effect on lidocaine plasma levels. Clinical implications include the need for dose adjustments or careful monitoring in patients with organ dysfunction.

Dosage Forms

Available Dosage Forms:
Xylocaine-MPF is available as a sterile injectable solution for parenteral administration. The preparation is commonly supplied as lidocaine hydrochloride in preservative-free formulations suitable for infiltration, nerve block, epidural, or intravenous administration.

Dosages for Adults and Adolescents:
For local anesthesia, lidocaine doses vary based on the site and procedure, commonly ranging from 20 mg to 300 mg per single administration, not exceeding a maximum total dose of approximately 4.5 mg/kg body weight without epinephrine. When used intravenously for cardiac arrhythmias such as ventricular tachycardia or ventricular fibrillation, an initial bolus of 1 to 1.5 mg/kg is typically administered, followed by continuous infusion of 1 to 4 mg/min adjusted based on patient response and toxicity signs.

Specific Patient Populations:
Dosage adjustments and caution are required in patients with hepatic impairment due to reduced metabolism, in elderly patients with comorbidities, and in those with severe cardiac conduction abnormalities. In obstetric use for epidural anesthesia during labor, dosages are carefully titrated to minimize systemic absorption and fetal exposure. Due consideration is given to patients with known hypersensitivity to amide-type local anesthetics or lidocaine formulations.

Mechanism Of Action

Lidocaine, the active component in Xylocaine-MPF, functions primarily as a local anesthetic by blocking voltage-gated sodium channels on neuronal cell membranes. By reversibly binding to specific sites within the sodium channel, lidocaine stabilizes the neuronal membrane and inhibits the rapid influx of sodium ions responsible for the initiation and propagation of action potentials. This blockade results in the loss of sensation including pain, temperature, and touch in the targeted region.

At the molecular level, lidocaine preferentially binds to the inactivated state of sodium channels, rendering neurons unable to depolarize or conduct impulses. This effect is dose-dependent and exhibits use-dependent blockade, meaning it is more potent in rapidly firing neurons, which is advantageous in selective suppression of pain signals.

In its role as an antiarrhythmic agent, lidocaine acts on cardiac myocytes by inhibiting abnormal electrical activity. It reduces the excitability of cardiac cells by blocking fast sodium channels during phase 0 of the cardiac action potential, thereby decreasing the rate of depolarization. Lidocaine is classified as a Class 1B antiarrhythmic, demonstrating rapid kinetics to shorten the action potential duration without significantly affecting conduction velocity in normal cardiac tissue. This helps suppress ventricular arrhythmias primarily in ischemic or damaged myocardial tissue.

Clinical and research studies have established lidocaine’s effectiveness in both peripheral anesthesia and emergency control of ventricular arrhythmias following myocardial infarction. Comparative to other local anesthetics such as bupivacaine or prilocaine, lidocaine has a moderate duration of action and rapid onset. Its safety profile, rapid metabolism, and adjustable dose regimens make it widely used in diverse medical procedures and cardiac management.

Pharmacological Actions

Reversible blockade of voltage-gated sodium channels on neuronal membranes, resulting in local anesthesia.
Use-dependent inhibition of neuronal action potential propagation, preferentially affecting rapidly firing neurons.
Class IB antiarrhythmic effect by blocking cardiac sodium channels, reducing ventricular excitability and suppressing arrhythmias.
Shortening of cardiac action potential duration in ischemic myocardial tissue without significant effect on normal conduction.
Rapid onset of action with moderate duration providing effective anesthesia for surgical and diagnostic procedures.
Metabolized rapidly in the liver producing active metabolites with less potency.
Decreases automaticity and excitability of cardiac Purkinje fibers.
Exertion of membrane-stabilizing effects, contributing to antiarrhythmic properties.
Blocks nerve conduction including pain, temperature, and tactile sensation.
Exhibits high lipid solubility enabling effective penetration through nerve membranes.
Minimal vasodilatory effects, which influence absorption rates and duration of action.
Ability to be administered via multiple routes: intravenous, local infiltration, epidural, and regional blocks.
Reduced systemic toxicity compared to some other local anesthetics due to rapid metabolism.
Provides epidural anesthesia reducing discomfort during labor by blocking afferent nerve signals.
Demonstrated efficacy in emergency management of ventricular tachycardia and ventricular fibrillation.

Therapeutic Or Clinical Uses

Local anesthesia for minor surgical procedures and diagnostic interventions.
Regional anesthesia including nerve blocks and epidural anesthesia, particularly during labor to relieve contractions.
Intravenous treatment of ventricular arrhythmias such as ventricular tachycardia and ventricular fibrillation.
Anesthetic agent for insertion of catheters, breathing tubes, or needle punctures to minimize procedural pain.
Management of postoperative pain when administered appropriately.
Used during dental procedures for numbness and analgesia.
Control of pain or discomfort in invasive diagnostic procedures requiring local or regional anesthesia.
Treatment of irregular heart rhythms to prevent cardiac arrest in emergency settings.
Facilitation of smooth conduction during surgical anesthesia by reducing nociceptive signals.
Adjunctive therapy for stabilizing cardiac electrical activity in myocardial infarction patients.
Numbing medication for minor burns, cuts, or lacerations under clinical supervision.
Reduction of discomfort in cystoscopy or endoscopic examinations using topical or infiltration routes.
Pain control during catheter insertions and vascular access procedures.
Used as a component of combination anesthesia techniques to enhance analgesic effects.
Provision of antiarrhythmic support during cardiac surgery or intensive care interventions.

Side Or Adverse Effects

Twitching, tremors, and seizures indicative of central nervous system excitation in toxicity.
Drowsiness and dizziness reflecting CNS depression or overdose effects.
Nausea and vomiting commonly associated with systemic absorption.
Confusion and disorientation, which may progress to unconsciousness in severe toxicity.
Tinnitus, blurred vision, and double vision signaling early neurotoxic effects.
Numbness in areas of accidental application beyond intended anesthetic site.
Respiratory depression or shallow breathing in cases of overdose.
Bradycardia and weak pulse reflecting cardiovascular depressive effects.
Hypotension secondary to peripheral vasodilation and myocardial depression.
Muscle stiffness and pain related to systemic toxic reactions.
Hypersensitivity reactions including hives, swelling, and anaphylaxis.
Skin bluish discoloration due to hypoxia during respiratory compromise.
Severe anxiety, unusual fear or uneasiness possibly related to CNS effects.
Light-headedness and syncope from cardiovascular or neurological adverse reactions.
Potential for allergic reactions especially in patients with known hypersensitivity to amide anesthetics.

Precautions

Use caution in patients with known hypersensitivity to lidocaine or other amide-type local anesthetics.
Monitor carefully in individuals with hepatic impairment due to reduced metabolism and increased toxicity risk.
Avoid use in severe heart block, Stokes-Adams syndrome, or Wolff-Parkinson-White syndrome.
Careful cardiovascular monitoring during intravenous administration to detect arrhythmias or conduction disturbances.
Caution in patients with compromised renal function, as metabolites may accumulate.
Avoid inadvertent intravascular injection during regional anesthesia to reduce systemic toxicity.
Use reduced dosages in elderly patients or those with comorbid cardiac and liver diseases.
Pregnancy and breastfeeding should be approached cautiously; use only if benefits justify potential risks.
Avoid administering in areas of infection or poor circulation to prevent unpredictable absorption.
Observe for signs of central nervous system toxicity especially during continuous infusions.
Inform patients about potential temporary numbness and precautions to prevent injury post procedure.
Monitor for allergic reactions, especially in patients with a history of corn allergy or other related allergies.
Ensure airway and resuscitation equipment availability in case of severe systemic reactions.
Titrate dosage carefully during labor epidurals to balance analgesia and maternal-fetal safety.
Avoid excessive cumulative dosing within short intervals to prevent overdose symptoms.

Warnings

Contraindicated in severe heart block due to risk of exacerbating conduction disturbances.
Do not use in patients with Stokes-Adams syndrome as lidocaine may worsen bradyarrhythmias.
Avoid in Wolff-Parkinson-White syndrome where abnormal conduction pathways can increase arrhythmia risk.
Risk of serious allergic reactions including anaphylaxis necessitates medical supervision.
Potential for CNS and cardiovascular toxicity with overdose or rapid systemic absorption.
Not recommended for use in patients with known hypersensitivity to amide local anesthetics.
Use in obstetric epidurals requires close monitoring to avoid fetal exposure and associated risks.
Avoid driving or operating machinery during and shortly after administration due to CNS effects.
Potential for respiratory depression requiring emergency interventions in overdose situations.
Risk of methemoglobinemia is rare but possible, requiring prompt recognition and treatment.
Use extra caution in patients with compromised cardiac function to avoid arrhythmogenic effects.
Monitoring with ECG is essential during intravenous use for arrhythmias to adjust dosing appropriately.
Avoid concomitant medications that may inhibit lidocaine metabolism increasing toxicity risk.
Inadvertent intravascular injection can cause immediate systemic toxicity and cardiovascular collapse.
Carefully evaluate risks before use in patients with malignant hyperthermia susceptibility.

Contraindication

Known allergy or hypersensitivity to lidocaine, amide-type local anesthetics, or components of the formulation.
Severe heart block without pacemaker support, due to risk of exacerbated conduction abnormalities.
Stokes-Adams syndrome, characterized by sudden slow heartbeats causing syncope.
Wolff-Parkinson-White syndrome, given the propensity for rapid arrhythmias.
Patients with a history of severe allergic reactions to numbing medications.
Use in conditions predisposing to cardiac conduction disturbances without appropriate monitoring.
Infection at the site of intended injection preventing safe local administration.
Patients with untreated congestive heart failure at high risk during systemic administration.
Known allergy to corn or corn products in formulations containing such excipients.
Avoid during pregnancy or breastfeeding unless clearly justified by clinical necessity.
Use not recommended in patients with severe hepatic failure due to impaired clearance.
Contraindicated in those with history of malignant hyperthermia triggered by anesthetic agents.
Intravenous administration contraindicated without appropriate equipment and trained personnel.
Avoid use in children for certain formulations without proper dosing adjustments and supervision.
Patients with seizures or CNS disorders may require cautious use due to potential CNS stimulation.

Drug Interactions

Cimetidine may inhibit hepatic metabolism of lidocaine, increasing plasma levels and toxicity risk.
Fluvoxamine and nefazodone, CYP450 inhibitors, can enhance lidocaine concentrations.
St John's Wort may induce metabolism and reduce lidocaine therapeutic levels.
Concurrent use of amiodarone requires careful monitoring due to additive cardiac effects.
Digoxin coadministration necessitates monitoring for cardiac arrhythmias.
Nicardipine and other calcium channel blockers may potentiate hypotensive and cardiac effects.
Procainamide, another antiarrhythmic, can interact increasing risk of arrhythmias and CNS toxicity.
Propranolol may reduce lidocaine clearance, increasing systemic exposure.
Antibiotics and antifungals, such as erythromycin or ketoconazole, may inhibit metabolism.
Antiviral agents for hepatitis or HIV/AIDS impacting CYP450 isoenzymes could alter lidocaine levels.
Antiepileptic drugs like carbamazepine and phenytoin may induce metabolism reducing efficacy.
Isoniazid and rifampin, tuberculosis medications, are enzyme inhibitors/inducers affecting levels.
Other CNS depressants can potentiate neurological side effects of lidocaine.
Drugs prolonging cardiac conduction or QT interval may have additive effects.
Herbal products may unpredictably impact lidocaine metabolism or pharmacodynamics.

Preparations Of The Drug

Sterile injectable solution of lidocaine hydrochloride preservative-free (MPF) for parenteral use.
Concentrations typically available include 0.5%, 1%, and 2% lidocaine hydrochloride solutions.
Formulated for infiltration, peripheral nerve block, epidural, and intravenous administration.
Preservative-free to allow for direct injection into sterile sites, including spinal and epidural spaces.
Single-use vials or ampoules for safe clinical administration minimizing contamination risk.
May come packaged with or without epinephrine/adrenaline to prolong anesthetic effect and reduce systemic absorption.
Available in various vial sizes ranging from 5 mL to 20 mL for appropriate dosing flexibility.
Supplied under the brand name Xylocaine-MPF ensuring medical-grade sterile anesthetic preparations.
Storage under controlled room temperature to maintain stability and efficacy.
Packaging includes precautions for handling and administration to avoid dosing errors.
Formulations free of preservatives ensure safety in sensitive CNS regional blocks.
Manufactured under strict quality control complying with pharmacopeial standards.
Labels include clear dosing instructions, indications, and warnings for clinical use.
Available as part of combination formulations with other agents for specialized anesthesia techniques.
Distributed for hospital and clinical use in emergency and procedural settings.