Lidocaine Parenteral

Introduction

Tradename: Xylocaine. (lidocaine hydrochloride) Class-IB antiarrhythmic agent.

Indications

• antiarrhythmic of choice for ventricular tachycardia (VT) or ventricular fibrillation (VF) that persists following defibrillation & administration of epinephrine
• also of benefit in stable VT & wide QRS complex tachycardias of uncertain type
• local anesthetic used for anesthesia & analgesia
• intravenous analgesia
  • neuropathic pain when opiates not effective
  • diabetic neuropathy
• post-herpetic neuralgia
• used as a last resort for status epilepticus
• skin irritation, superficial injury
• pruritus, dermatitis
• eye surgery
• gag reflex

Contraindications

• 3rd degree heart block with a ventricular escape rhythm
• Wolf-Parkinson-White syndrome
• Stokes-Adams syndrome

Dosage

Load:

• 1-1.5 mg/kg IV (generally 100 mg), then 0.5 mg/kg every 8-10 min, max 3 mg/kg

Caution:

• initial bolus should be reduced 50% in patients with:
  • heart failure
  • shock
  • hepatic dysfunction

Maintenance:

• 1-3 mg/kg/hr, 2 mg in 250 mL D5W (8 mg/mL)* at 1-4 mg/min (7-30 mL/hr)

Pediatrics:

• 20-50 ug/kg/min, 10 kg: 3 mL/hr = 40 ug/kg/min

* a concentration >= 40 mg/mL is needed for PCA pump because the total volume must be < 3 mL/hour

Status epilepticus:

• bolus: 1 mg/kg followed in 5 min by 0.5 mg/kg
• infusion: 1-2 mg/min

Injection: 0.05% (5 mg/mL) (50 mL) 1% (10 mg/mL) (5, 10, 30, 50 mL) 2% (20 mg/mL) (5 & 50 mL) 4% (40 mg/mL) (5 mL) 20% (200 mg/mL) (5 & 10 mL)

7.5% in 5% dextrose (75 mg/mL) (2 mL)

Injection with endotracheal cannulation: (Duo-Trach) 4% (40 mg/mL) (5 mL) (max 2-4 mg/kg)

Pharmacokinetics

• anesthetic
  • well absorbed by tissue
  • faster absorption is associated with a shorter duration of action
  • addition of epinephrine prolongs the action & localizes the anesthesia
  • distributes to all tissues
  • crosses the blood brain barrier
  • metabolized by the liver
  • eliminated in the urine
  • acidification of the urine increases the rate of elimination
• analgesic
  • therapeutic level is 2-6 ug/mL for analgesia
• antiarrhythmic
  • onset of action 45-90 seconds
  • duration of action 10-20 minutes
  • therapeutic level is 1-5 ug/mL
  • well distributed to all tissue
  • volume of distribution
    • decreased in CHF
    • increased in liver disease
  • crosses the blood-brain barrier
  • 1/2life
    • initial: 7-30 minutes
    • terminal 1.5-2 hours
  • metabolized by the liver to MEGX & GX both of which are active metabolites

Adverse effects

• not common (1-10%)
  • positional headache, hypotension, shivering
• central nervous system (< 1%)
  • confusion, seizures, respiratory arrest, agitation, tremors, psychosis, drowsiness, visual disturbances, lethargy, euphoria, slurred speech, hallucinations
• cardiac (< 1%)
  • negative inotropic effects at high doses
  • arrhythmias
    • sinus arrest
    • AV block
    • increased AV conduction in atrial fibrillation/flutter
    • hypotension
• other (< 1%)
  • urticaria, paresthesias, nausea/vomiting, tinnitus, dyspnea, itching, rash
• adverse effects by serum blood levels (in parentheses)
  • transient adverse effects within therapeutic range
    • lightheadedness (1 ug/mL)
    • peri-oral numbness (2 ug/mL)
    • metallic taste (2-3 ug/mL)
    • tinnitus (5-6 ug/mL)
  • indications for stopping lidocaine infusion
    • blurry vision (6 ug/mL)
    • twitching (8 ug/mL)
    • convulsions (10 ug/mL)
    • cardiac depression (20-25 ug/mL)

Drug interactions

• serum 1/2 life of lidocaine is prolonged by:
  • propranolol
  • cimetidine
• agents which increase metabolism of lidocaine
  • phenobarbital
  • phenytoin
• agents which decrease cardiac output or hepatic blood flow probably decrease lidocaine clearance
  • propranolol
  • anesthetics
  • norepinephrine

• drug interaction(s) of antiarrhythmic agents in combination with diuretics
• drug interaction(s) of beta-adrenergic receptor antagonists with lidocaine

Laboratory

• specimen:
  • serum, plasma (heparin, EDTA)
  • collect > 30 minutes after a bolus dose
  • stable at neutral pH for 1 year at -20 degrees C
• methods: HPLC, GLC, GC-MS, EIA, FPIA
• interferences:
  • some GLC methods lack sensitivity & specificity
  • do NOT collect in serum separator tubes; lidocaine may be extracted by the separator gel

Mechanism of action

• local anesthetic
  • amide-type local anesthetic
  • reversible blocks nerve conduction in all nerve fibers (sensory, motor, autonomic) by decreasing permeability of nerve to Na+
  • decreases rate of nerve depolarization
  • increases threshold of excitability
  • prevents propagation of action potential
  • autonomic activity is lost 1st followed by sensory & motor function
• antiarrhythmic
  • class 1B antiarrhythmic agent
  • decreases phase 0
  • decreases action potential duration
  • decreases phase 4
  • suppresses automaticity in the His-Purkinje system
  • suppresses depolarization of the ventricles during diastole

More general terms

• lidocaine (Xylocaine)
• parenteral agent
• antiarrhythmic agent, Group IB