Lidocaine

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Contents 1 Introduction 2 Indications 3 Contraindications 4 Dosage 5 Pharmacokinetics 6 Adverse-effects 7 Drug-interactions 8 Laboratory 9 Mechanism-of-action 10 More General Terms 11 Additional Terms 12 Internet Database 13 References

Introduction

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

Indications

• antiarrhythmic of choice in the treatment of 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

• used as a last resort for status epilepticus

Contraindications

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

• pregnancy category = b
• safety in lactation = ?

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)
• Local anesthetic: 0.5%, 1%, 1.5%, 2%, 4%, 10%, 20%. with epinephrine 0.5%, 1%, 1.5%, 2%.
• Viscous lidocaine: (2%) (100 mL) Indications: esophageal pain: 15 mL ( swallow)
• Injection with endotracheal cannulation: ( Duo-Trach) 4% (40 mg/mL) (5 mL) (max 2-4 mg/kg)
• Ointment: (topical) 5% (35 g)
• Solution: (topical) 4% (50 mL)

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
  

• elimination via liver 90 %
• elimination via kidney 10 %
• 1/2life = 1.5-2.0 hours
• protein binding = 43-59 %
• elimination by hemodialysis = -

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

• amide
• amine
• local anesthetic
• antiarrhythmic agent, Group IB

Additional Terms

• glycinexylidide (GX)
• lidocaine test
• monoethylglycinexylidide (MEGX, Ethylglycylxylidide)

Internet Database

PubChem: 3676
PubChem: 3924

References

1. Manual of Medical Therapeutics, 28th ed, Ewald & McKenzie (eds), Little, Brown & Co, Boston, 1995, pg 155, 173
2. Advanced Cardiac Life Support, The American Heart Association 1994
3. Harrison's Principles of Internal Medicine, 13th ed. Isselbacher et al (ed), Companion Handbook, McGraw Hill, NY, 1994
4. Drug Information & Medication Formulary, Veterans Affairs, Central California Health Care System, 1st ed., Ravnan et al eds, 1998
5. Kaiser Permanente Northern California Regional Drug Formulary, 1998
6. Clinical Guide to Laboratory Tests, 3rd ed. Teitz ed., W.B. Saunders, 1995
7. Frederich M., UCLA Multicampus Program in Geriatrics & Gerontology, Syllabus: The Cutting Edge in Palliative Medicine, 2001

lidocaine (Xylocaine)