Introduction
Xylocaine (lidocaine hydrochloride) is a widely used amide-type local anesthetic and antiarrhythmic medication. First introduced in 1948, it remains one of the most commonly administered local anesthetics in clinical practice. Xylocaine is available in various formulations including injectable solutions, topical preparations, and transdermal delivery systems, making it versatile for both regional anesthesia and systemic applications.
Mechanism of Action
Xylocaine exerts its pharmacological effects by blocking voltage-gated sodium channels in neuronal membranes. This action stabilizes the neuronal membrane and prevents the initiation and conduction of nerve impulses, resulting in local anesthesia. As a class IB antiarrhythmic, it shortens the action potential duration and effective refractory period in cardiac tissues by preferentially binding to sodium channels in their inactivated state.
Indications
FDA-approved indications:- Local anesthesia via infiltration, nerve block, epidural, and spinal routes
- Topical anesthesia for mucous membranes and skin
- Ventricular arrhythmias (particularly following myocardial infarction)
- Dental anesthesia
- Neuropathic pain management
- Postherpetic neuralgia (topical formulations)
- Procedural sedation adjunct
Dosage and Administration
Local Anesthesia:- Infiltration: 0.5-1% solution, max 4.5 mg/kg (not to exceed 300 mg)
- Epidural: 1-2% solution, 25-300 mg based on procedure
- Dental: 2% solution with epinephrine 1:50,000-1:100,000
- IV loading: 1-1.5 mg/kg, followed by infusion of 1-4 mg/min
- Maximum dose: 3 mg/kg over 1 hour
- Hepatic impairment: Reduce dose by 50%
- Renal impairment: No significant adjustment needed
- Elderly: Reduce dose due to decreased clearance
- Pediatrics: 0.5-1.0 mg/kg for arrhythmias
Pharmacokinetics
Absorption: Well-absorbed from mucous membranes; incomplete GI absorption due to first-pass metabolism Distribution: Vd: 1-2 L/kg; crosses placenta and blood-brain barrier Metabolism: Extensive hepatic metabolism via CYP3A4 and CYP1A2 to active metabolites (MEGX, GX) Elimination: Half-life: 1.5-2 hours; renal excretion (90% as metabolites) Protein binding: 60-80% primarily to alpha-1-acid glycoproteinContraindications
- Hypersensitivity to amide-type local anesthetics
- Adams-Stokes syndrome
- Wolff-Parkinson-White syndrome
- Severe heart block (second or third degree) without pacemaker
- Concurrent use with class III antiarrhythmic agents
- Septicemia at injection site (for regional anesthesia)
Warnings and Precautions
Black Box Warning: Cardiac arrest and death have occurred with improper use of IV formulation- Risk of systemic toxicity: CNS effects (seizures, coma) and cardiovascular collapse
- Methemoglobinemia risk (especially with prilocaine-containing preparations)
- Use caution in patients with:
- Severe hepatic impairment - Heart failure - Hypoxia - Hyperkalemia - Respiratory depression
- Epinephrine-containing formulations contraindicated in end-arterial locations
Drug Interactions
Major interactions:- Beta-blockers: Increased risk of bradycardia and hypotension
- CYP3A4 inhibitors (ketoconazole, erythromycin): Increased lidocaine levels
- Class I and III antiarrhythmics: Additive cardiac effects
- Succinylcholine: Prolonged neuromuscular blockade
- CYP3A4 inducers (rifampin, phenytoin): Decreased lidocaine efficacy
- Local anesthetics: Additive toxic effects
Adverse Effects
Common (≥1%):- Application site reactions (erythema, edema)
- Lightheadedness
- Drowsiness
- Nausea
- Paresthesia
- Cardiovascular: Bradycardia, hypotension, cardiac arrest
- CNS: Seizures, respiratory depression
- Hematologic: Methemoglobinemia
- Allergic: Anaphylaxis (rare)
- Otic: Tinnitus (early sign of toxicity)
Monitoring Parameters
- Vital signs (especially during IV administration)
- ECG monitoring during antiarrhythmic use
- Neurological status
- Signs of local tissue irritation (topical use)
- Serum levels (therapeutic range: 1.5-5 mcg/mL for arrhythmias)
- Oxygen saturation (for methemoglobinemia risk)
Patient Education
- Report any signs of allergic reaction: rash, itching, swelling
- Avoid driving or operating machinery until effects wear off
- Do not apply topical preparations to broken skin or large areas
- Inform all healthcare providers of Xylocaine use
- For dental procedures: Avoid eating until sensation returns
- Report any chest pain, palpitations, or dizziness immediately
- Store preparations away from children and heat
References
1. FDA Prescribing Information: Xylocaine (2023) 2. Miller RD, et al. Miller's Anesthesia. 9th ed. Elsevier; 2020 3. Brunton LL, et al. Goodman & Gilman's The Pharmacological Basis of Therapeutics. 13th ed. McGraw-Hill; 2023 4. Neal JM, et al. The ASRA Practice Advisory on Local Anesthetic Systemic Toxicity. Reg Anesth Pain Med. 2022;47(1):1-10 5. El-Boghdadly K, et al. Local Anesthetic Systemic Toxicity: Current Perspectives. Local Reg Anesth. 2023;16:25-34 6. Lexicomp Online. Lidocaine Drug Monograph. Wolters Kluwer; 2024