AHFS Class:

• Class Ib Antiarrhythmics 24:04.04.08

Generic Name(s):

• Lidocaine Hydrochloride

Lidocaine hydrochloride is an amide-type local anesthetic that is also used as a class Ib antiarrhythmic agent.

Ventricular Arrhythmias

Ventricular Arrhythmias Associated with Myocardial Infarction or Cardiac Manipulation

Lidocaine hydrochloride is used parenterally as an alternative to other antiarrhythmic drugs (e.g., amiodarone, procainamide, sotalol) for the acute treatment of life-threatening ventricular arrhythmias such as those that occur following myocardial infarction (MI) or during cardiac manipulative procedures such as cardiac surgery.400,401,500 Lidocaine previously was recommended for the prevention of ventricular arrhythmias associated with acute myocardial ischemia or infarction.400 Such use was supported largely by animal studies and extrapolation from historical use of the drug to suppress premature ventricular contractions (PVCs) and prevent ventricular fibrillation and potentially, sudden death, following acute MI.52,118,126 However, although pooled analysis of randomized controlled trials of prophylaxis with lidocaine demonstrated a reduction of approximately 33% in primary ventricular fibrillation following acute MI, this benefit was offset by a trend toward increased mortality, probably as a result of fatal episodes of bradycardia and asystole.119,126,400 Therefore, experts no longer recommend routine prophylactic use of lidocaine during acute MI, and such use has largely been abandoned.400,527

Shock-Resistant Ventricular Fibrillation or Pulseless Ventricular Tachycardia

Lidocaine is used as adjunctive therapy for the management of ventricular fibrillation or pulseless ventricular tachycardia resistant to cardiopulmonary resuscitation (CPR), defibrillation, and a vasopressor (e.g., epinephrine).400,401

Antiarrhythmic drugs are used during cardiac arrest to facilitate the restoration and maintenance of a spontaneous perfusing rhythm in patients with refractory (i.e., persisting or recurring after at least one shock) ventricular fibrillation or pulseless ventricular tachycardia; however, there is no evidence that these drugs increase survival to hospital discharge when given routinely during cardiac arrest.400 High-quality CPR and defibrillation are integral components of ACLS and the only proven interventions to increase survival to hospital discharge.400,401 Other resuscitative efforts, including drug therapy, are considered secondary and should be performed without compromising the quality and timely delivery of chest compressions and defibrillation.400,401 The principal goal of pharmacologic therapy during cardiac arrest is to facilitate return of spontaneous circulation (ROSC), and epinephrine is the drug of choice for this use.400,401 (See Uses: Advanced Cardiovascular Life Support and Cardiac Arrhythmias, in Epinephrine 12:12.12.) If an antiarrhythmic agent is needed for the treatment of refractory ventricular fibrillation or pulseless ventricular tachycardia during adult cardiac arrest, AHA recommends amiodarone as the first-line drug of choice because of its proven benefits in improving rates of ROSC and hospital admission; lidocaine may be used as an alternative.401 Results of several studies suggest that amiodarone is more effective than lidocaine in improving rates of ROSC and hospital admission in patients with shock-refractory ventricular fibrillation or pulseless ventricular tachycardia.401 In pediatric advanced life support (PALS), current evidence supports the use of either amiodarone or lidocaine for these arrhythmias.402

In a randomized, double-blind, comparative study, approximately 23% of patients with out-of-hospital cardiac arrest due to defibrillation-refractory ventricular arrhythmias (i.e., ventricular fibrillation, pulseless ventricular tachycardia) who received IV amiodarone hydrochloride (5 mg/kg) or lidocaine-placebo survived to hospital admission compared with 12% of those who received IV lidocaine hydrochloride (1.5 mg/kg) or amiodarone-placebo following at least 3 precordial electrical shocks, IV epinephrine, and an additional precordial shock.127 Among patients for whom the time from dispatch of the ambulance to the administration of the drug was equal to or less than the median time (24 minutes), approximately 28% of those given amiodarone and 15% of those given lidocaine survived to hospital admission.127 Despite these results, only about 6 or 4% of patients receiving IV amiodarone or IV lidocaine, respectively, who survived to hospital admission lived to be discharged from the hospital.127 Evidence supporting the use of amiodarone and lidocaine in pediatric cardiac arrest is more limited and principally based on extrapolation of data from the adult population.402,459 In a retrospective cohort study that included data from 889 pediatric patients with in-hospital cardiac arrest, improved ROSC was observed with lidocaine compared with amiodarone.402 Neither drug was associated with improved survival to hospital discharge.402,459

Monomorphic Ventricular Tachycardia

Lidocaine may be considered as an alternative to other antiarrhythmic agents or synchronized cardioversion for the treatment of hemodynamically stable monomorphic ventricular tachycardia; however, other agents are preferred.401 Available evidence suggests that lidocaine is less effective in treating ventricular tachycardia than either procainamide, sotalol, or amiodarone.401

Status Epilepticus

IV lidocaine has been used as a last resort for the treatment of status epilepticus†.

Local Anesthesia

For the use of lidocaine hydrochloride as a local anesthetic, see Lidocaine 72:00.

Administration

Parenteral Administration

Lidocaine hydrochloride is administered IV for the treatment of ventricular arrhythmias. The drug also has been administered by IM injection, but an IM formulation no longer is commercially available in the US. Lidocaine hydrochloride also has been administered by intraosseous (IO) injection† in the setting of advanced cardiovascular life support (ACLS) when IV administration is not possible; onset of action and systemic concentrations of the drug are comparable to those achieved with venous administration.400,401 Lidocaine solutions that contain epinephrine must not be used to treat arrhythmias.

Lidocaine hydrochloride also is available as solutions of the drug in 5% dextrose. Contents of lidocaine hydrochloride in dextrose injections should be inspected visually for discoloration and/or particulate matter prior to administration whenever solution and container permit. Additives should not be introduced into the solution container. Lidocaine hydrochloride in dextrose injection should not be used in series connections with other plastic containers, since such use could result in air embolism from residual air being drawn from the primary container before administration of fluid from the secondary container is complete. Commercially available solutions of the drug in 5% dextrose should not be administered unless the solution is clear and the container and seals are undamaged. When the commercially available IV infusion solution of lidocaine hydrochloride and 5% dextrose is used, the accompanying labeling should be consulted for proper methods of administration and other associated precautions.

Standardize 4 Safety

Standardized concentrations for lidocaine hydrochloride have been established through Standardize 4 Safety (S4S), a national patient safety initiative to reduce medication errors, especially during transitions of care. 249,250Multidisciplinary expert panels were convened to determine recommended standard concentrations. 249,250Because recommendations from the S4S panels may differ from the manufacturer's prescribing information, caution is advised when using concentrations that differ from labeling, particularly when using rate information from the label. 249,250 For additional information on S4S (including updates that may be available), see [Web].249,250

Endotracheal Administration

Lidocaine hydrochloride may be administered via the endotracheal route† if vascular (IV or IO) access cannot be established during cardiac arrest; however, IV or IO administration is preferred whenever possible because of more predictable drug delivery and pharmacologic effect.401,403 (See Pharmacokinetics: Absorption.) For endotracheal administration in adults, the dose should be diluted in 5-10 mL of 0.9% sodium chloride or sterile water and administered directly into the endotracheal tube.401 In pediatric patients, the endotracheal dose should be followed with a flush of at least 5 mL of 0.9% sodium chloride injection.403 Absorption of lidocaine, when administered via an endotracheal tube, may be increased by diluting the drug in sterile water instead of 0.9% sodium chloride.401

Dosage

Dosage of lidocaine hydrochloride must be carefully adjusted according to individual requirements and response.

Ventricular Arrhythmias

Adult Dosage

For the initial treatment of ventricular arrhythmias, lidocaine hydrochloride usually is administered as a rapid (i.e., bolus) IV injection. The manufacturer states that the usual adult dose of lidocaine hydrochloride is 50-100 mg administered at a rate of approximately 25-50 mg/minute by direct IV injection.500 If the desired response is not achieved, a second dose may be administered 5 minutes after completion of the first injection.500 The manufacturer states that no more than 200-300 mg should be administered during a 1-hour period. 500 Patients with congestive heart failure or cardiogenic shock may require smaller loading doses.

For the treatment of hemodynamically stable monomorphic ventricular tachycardia, the American Heart Association (AHA) recommends an initial adult dose of 1-1.5 mg/kg IV; additional doses of 0.5-0.75 mg/kg may be administered every 5-10 minutes as necessary, up to a maximum total dose of 3 mg/kg.401

For the treatment of shock-resistant ventricular fibrillation or pulseless ventricular tachycardia during cardiac resuscitation, the initial adult loading dose of lidocaine hydrochloride is 1-1.5 mg/kg by IV or IO† injection,401 followed by 0.5-0.75 mg/kg repeated at 5- to 10-minute intervals as necessary, up to a maximum total dose of 3 mg/kg.401

If IV or IO† access cannot be established during cardiac arrest, lidocaine may be administered via the endotracheal† route.401 Although the optimum endotracheal dose of lidocaine hydrochloride remains to be established, some experts state that typical doses should be 2-2.5 times those administered IV, and generally should be diluted in 5-10 mL of 0.9% sodium chloride or sterile water.401

A maintenance infusion of lidocaine hydrochloride may be required to maintain normal sinus rhythm if oral antiarrhythmic therapy is not feasible. Following initial administration with direct IV injections, an IV infusion of lidocaine hydrochloride may be initiated at a rate of 1-4 mg/minute (14-57 mcg/kg per minute).401,500 Some clinicians recommend maintaining the infusion rate below 30 mcg/kg per minute in patients with congestive heart failure. In patients with liver disease, dosing must be carefully individualized.32,107,108,109,110,111,112,113,114,115,116

Major differences in lidocaine pharmacokinetics may exist for different types of liver disease (e.g., cirrhosis, hepatitis) and no consistent correlation has been established between clearance of the drug and severity of liver disease (as determined by liver function tests).32,107,108,109,110,111,112,113,114,115,116 No dosing modification appears to be necessary in patients with renal failure.

When arrhythmias reappear during a constant infusion of lidocaine hydrochloride, a small bolus dose (e.g., 0.5 mg/kg) may be given to rapidly increase plasma concentrations of the drug; the infusion rate is maintained or increased simultaneously. If the infusion rate alone is increased, a plateau or peak concentration of lidocaine may not be reached for 3-4 half-lives (5-8 hours).

The infusion should be terminated as soon as the patient's basic cardiac rhythm appears to be stable or at the earliest sign of toxicity. If signs of excessive cardiac depression, such as prolongation of the PR interval and QRS complex or the appearance or aggravation of arrhythmias occur, the infusion should be stopped immediately. The manufacturers state that it should rarely be necessary to continue the infusion for longer than 24 hours. Clinical studies have reported continuation of lidocaine infusions for several days; however, there are data which indicate that the half-life of lidocaine may be increased to 3 hours or longer following infusions lasting longer than 24 hours, and dosage may need to be reduced accordingly (e.g., by 50%) to avoid accumulation of the drug and potential toxicity. If maintenance therapy is necessary, therapy should be changed to an oral antiarrhythmic agent.

Pediatric Dosage

Controlled clinical studies to establish pediatric dosing schedules of lidocaine hydrochloride have not been performed.100 Some clinicians have suggested that infants and children may be given an initial rapid IV injection (i.e., bolus) of 0.5-1 mg/kg; this dose may be repeated according to the response of the patient, but the total dose should not exceed 3-5 mg/kg. A maintenance IV infusion of 10-50 mcg/kg per minute may be given via an infusion pump.

For the treatment of shock-refractory ventricular fibrillation or pulseless ventricular tachycardia during pediatric resuscitation, the recommended dosage of lidocaine hydrochloride is an initial rapid IV or IO† injection (i.e., bolus) of 1 mg/kg, followed by a maintenance infusion of 20-50 mcg/kg per minute.402,403 A repeat IV injection should be given if there is more than a 15-minute delay from the time of the initial rapid IV injection dose to the onset of the infusion.402

If IV or IO† access cannot be established, lidocaine may be administered via the endotracheal† route.403 Although the optimum endotracheal dose of lidocaine hydrochloride remains to be established, some experts state that typical doses should be 2-2.5 times those administered IV.403 If cardiopulmonary resuscitation (CPR) is in progress, chest compressions should be interrupted briefly to administer lidocaine.403 Following administration, the endotracheal tube should be flushed with 5 mL of 0.9% sodium chloride injection and followed by 5 consecutive positive-pressure ventilations.403

Status Epilepticus

For the treatment of status epilepticus†, some clinicians have suggested an initial IV lidocaine hydrochloride bolus dose of 1 mg/kg. If the seizure is not terminated, 0.5 mg/kg may be given 2 minutes after completion of the first injection. A maintenance IV infusion of 30 mcg/kg per minute has been given to prevent recurrence of seizures.

Serious adverse reactions to lidocaine are uncommon. Adverse effects of the drug mainly involve the CNS, are usually of short duration, and are dose related.

If severe reactions occur, lidocaine administration should be discontinued; emergency resuscitative procedures and other supportive measures should be instituted. Maintenance of adequate ventilation and a patent airway are of primary importance. For the treatment of severe seizures, small IV doses of diazepam or an ultrashort-acting barbiturate (e.g., thiopental, thiamylal) may be given or, if these are not available, pentobarbital or secobarbital may be administered. If the patient is anesthetized, a short-acting neuromuscular blocking agent (e.g., succinylcholine) may be given IV. If circulatory depression occurs, IV fluids and vasopressors such as ephedrine or metaraminol may be used if necessary.

Nervous System Effects

Adverse CNS reactions may be manifested by drowsiness;128 dizziness; disorientation;128 confusion; lightheadedness; tremulousness; psychosis; nervousness; apprehension; agitation; euphoria; tinnitus; visual disturbances including blurred or double vision; nausea; vomiting; paresthesia; sensations of heat, cold, or numbness; difficulty swallowing; dyspnea; and slurred speech.128 Muscle twitching128 or tremors, seizures,128 unconsciousness or altered consciousness,128 coma, and respiratory depression and arrest may also occur.

Dermatologic and Sensitivity Reactions

Hypersensitivity to lidocaine is rare and may be characterized by skin lesions, urticaria, edema, and anaphylactoid reactions.

Cardiovascular Effects

Although usual doses of lidocaine generally produce no adverse cardiovascular effects, patients with high plasma concentrations of the drug or myocardial conduction defects may develop hypotension, arrhythmias, heart block, cardiovascular collapse, and bradycardia128 which may lead to cardiac arrest. However, cardiac arrest caused by lidocaine is usually secondary to respiratory arrest. In anesthetized patients, CNS toxicity and seizures may not occur; cardiovascular depression may be the first manifestation of toxicity in these patients.

Administration Effects

Local thrombophlebitis may occur in patients receiving prolonged IV infusions of lidocaine.

Precautions and Contraindications

Constant ECG monitoring is necessary during IV administration of lidocaine. ECG changes such as prolongation of the PR interval and QRS complex or the appearance or aggravation of arrhythmias necessitates prompt cessation of lidocaine infusion. Resuscitative equipment and drugs should be immediately available for the management of severe, adverse cardiovascular, respiratory, or CNS effects. If severe reactions occur, lidocaine should be discontinued and appropriate therapy instituted. Severe reactions are often preceded by somnolence and paresthesia, and these symptoms should not be ignored.

Although the manufacturers state that lidocaine should be used with caution in patients with severe renal disease, the drug has been used safely in these patients. Lidocaine should be administered with caution to patients with liver disease, congestive heart failure, marked hypoxia, severe respiratory depression, hypovolemia, or shock. Caution should be used when administering lidocaine to patients with sinus bradycardia or incomplete heart block for the treatment of ventricular premature contractions without prior acceleration of heart rate, since more frequent and serious ventricular arrhythmias or heart block may result. In addition, use of the drug in patients with symptomatic bradycardia may result in potentially life-threatening adverse effects (e.g., death), particularly if the bradycardia is a ventricular escape rhythm that is mistaken for preventricular contractions or slow ventricular tachycardia. Lidocaine may increase ventricular rate when it is administered to patients with atrial fibrillation. Hypokalemia, hypoxia, and disorders of acid-base balance must be eliminated as potentiating factors in patients who require large doses of antiarrhythmic agents to control ventricular irritability.

Lidocaine is contraindicated in patients with a known hypersensitivity to the amide-type local anesthetics. There have been no reports of cross-sensitivity reactions between lidocaine and procainamide or quinidine. Lidocaine should be used with caution in patients with any form of heart block and is contraindicated in patients with Adams-Stokes syndrome or with severe degrees of SA, AV, or intraventricular heart block in the absence of an artificial pacemaker. Although some manufacturers state that lidocaine is contraindicated in patients with Wolff-Parkinson-White syndrome, some clinicians have used the drug for the treatment of tachyarrhythmias in patients with this syndrome.

Pediatric Precautions

Safety and efficacy of lidocaine in the management of ventricular arrhythmias in children have not been established by controlled clinical studies.100 However, lidocaine has been used for the treatment of ventricular arrhythmias in infants and children.402,403 Some experts state that use of the drug may be considered during pediatric resuscitation for the treatment of ventricular fibrillation or pulseless ventricular tachycardia that is resistant to cardiopulmonary resuscitation (CPR), cardioversion (i.e., defibrillation), and epinephrine.402,403

Pregnancy and Lactation

Pregnancy

Safe use of lidocaine during pregnancy (prior to labor) has not been established. The drug should be used during pregnancy only when clearly needed.

Lactation

Since lidocaine is distributed into milk,117 the drug should be used with caution in nursing women.100 Limited data suggest that the amount of drug that potentially would be ingested by a breast-fed infant is small.117

Succinylcholine

In anesthetized individuals, the neuromuscular blocking effect of succinylcholine has been reported to be increased by IV administration of lidocaine prior to or following succinylcholine administration; however, this effect appears to be important only following administration of lidocaine in doses higher than those usually used clinically.

Antiarrhythmic Agents

When lidocaine is administered with other antiarrhythmic drugs such as phenytoin, procainamide, propranolol, or quinidine, the cardiac effects may be additive or antagonistic and toxic effects may be additive. Phenytoin may stimulate the hepatic metabolism of lidocaine, but the clinical importance of this effect is not known.

Other Drugs

Concurrent use of lidocaine with cimetidine or propranolol may result in increased serum concentrations of lidocaine with resultant toxicity. Cimetidine and propranolol substantially reduce the systemic clearance of lidocaine, apparently by reducing hepatic blood flow and hepatic extraction of the drug; other mechanisms (e.g., altered distribution or metabolism of lidocaine) may also be involved. If lidocaine and cimetidine or propranolol are used concurrently, the patient should be closely observed for signs of lidocaine toxicity, and serum lidocaine concentrations should be carefully monitored; reduction of lidocaine dosage may be necessary.

Pharmacology

Lidocaine hydrochloride is an amide-type local anesthetic that is also used as an antiarrhythmic agent. The cardiac actions of lidocaine appear to be similar to those of phenytoin. Lidocaine is considered a class I (membrane-stabilizing) antiarrhythmic agent. Like other class I antiarrhythmic agents, lidocaine is believed to combine with fast sodium channels in their inactive state and thereby inhibit recovery after repolarization in a time- and voltage-dependent manner which is associated with subsequent dissociation of the drug from the sodium channels. Lidocaine exhibits electrophysiologic effects characteristic of class IB antiarrhythmic agents. The electrophysiologic characteristics of the subgroups of class I antiarrhythmic agents may be related to quantitative differences in their rates of attachment to and dissociation from transmembrane sodium channels, with class IB agents exhibiting rapid rates of attachment and dissociation.

Lidocaine controls ventricular arrhythmias by suppressing automaticity in the His-Purkinje system and by suppressing spontaneous depolarization of the ventricles during diastole.128 These effects occur at lidocaine concentrations that do not suppress automaticity of the sinoatrial (SA) node. At therapeutic plasma concentrations, lidocaine has little effect on atrioventricular (AV) node conduction and His-Purkinje conduction in the normal heart. Specialized conducting tissues of the atria are less sensitive to the effects of lidocaine than are those of ventricular tissues. Lidocaine has a variable effect on the effective refractory period (ERP) of the AV node; the drug shortens the ERP and the action potential duration of the His-Purkinje system. Lidocaine does not appear to affect excitability of normal cardiac tissue.

Unlike quinidine and procainamide, lidocaine has little effect on autonomic tone and generally does not produce a substantial fall in blood pressure, decreased myocardial contractility, or diminished cardiac output in usual doses. Although lidocaine usually has little effect on heart rate, patients with a diseased or abnormal sinus node may be especially sensitive to the cardiac depressant effects of the drug. Lidocaine may increase coronary blood flow in patients with recent myocardial infarction.

Lidocaine is a CNS depressant and produces sedative, analgesic, and anticonvulsant effects. With high doses, seizures may result from depression of inhibitory influences on motor pathways; severe overdosage may cause respiratory arrest because of motor nerve paralysis and/or inadequate medullary blood flow. Lidocaine also suppresses the cough and gag reflexes.

Pharmacokinetics

Absorption

Although lidocaine hydrochloride is absorbed from the GI tract, it passes into the hepatic portal circulation and only about 35% of an oral dose reaches systemic circulation unchanged. One study showed that therapeutic plasma concentrations are not achieved after oral administration of 250 or 500 mg of the drug, but toxic effects appear, perhaps because of high concentrations of toxic metabolites.

Plasma lidocaine concentrations of approximately 1-5 mcg/mL are required to suppress ventricular arrhythmias. Toxicity has been associated with plasma lidocaine concentrations greater than 5 mcg/mL. Following IV administration of a bolus dose of 50-100 mg of lidocaine hydrochloride, the drug has an onset of action within 45-90 seconds and a duration of action of 10-20 minutes. If an IV infusion is initiated without an initial bolus dose, the attainment of therapeutic plasma concentrations is relatively slow. For example, therapeutic plasma concentrations are achieved in 30-60 minutes after the start of a continuous infusion of 60-70 mcg/kg per minute when no loading dose is given. Plasma concentrations of 1.5-5.5 mcg/mL have been reported to be maintained with an initial IV bolus of 1.5 mg/kg followed by infusion of 50 mcg/kg per minute in patients with heart disease.

Lidocaine hydrochloride is absorbed in the trachea; when the drug is administered endotracheally, plasma concentrations generally are lower than those achieved with vascular administration.401,458 A biphasic pattern of absorption is observed following endotracheal administration of lidocaine (initial instantaneous absorption of a small fraction of the dose, followed by a late, delayed absorption phase).458 Absorption may be increased by diluting the drug in sterile water instead of 0.9% sodium chloride injection.401

After intradeltoid injection (an IM formulation no longer is commercially available in the US) of lidocaine hydrochloride 4.5 mg/kg in one study in patients with ventricular premature contractions, peak blood concentrations of 2.9 mcg/mL were achieved in 10 minutes and blood concentrations of 2.2 mcg/mL persisted for 60 minutes. Intradeltoid injection produces higher blood concentrations and more rapid development of peak blood concentrations than do injections into the gluteus maximus or vastus lateralis.

Distribution

Lidocaine is widely distributed into body tissues. After an IV bolus, there is an early, rapid decline in plasma concentrations of the drug, principally associated with distribution into highly perfused tissues such as the kidneys, lungs, liver, and heart, followed by a slower elimination phase in which metabolism and redistribution into skeletal muscle and adipose tissue occur. Lidocaine has a high affinity for fat and adipose tissue. As plasma concentrations of the drug fall, the diffusion gradient from tissue to blood increases and the lidocaine that initially entered the highly perfused tissues and fat diffuses back into the blood. The volume of distribution is decreased in patients with congestive heart failure and increased in patients with liver disease.

Binding of lidocaine to plasma proteins is variable and concentration dependent.100,101,102,103,104,105 At concentrations of 1-4 mcg/mL, the drug is approximately 60-80% bound to plasma proteins.100,101,102,103,104,105 Lidocaine is partially bound to α₁-acid glycoprotein (α₁-AGP), and the extent of binding to α₁-AGP depends on the plasma concentration of the protein.100,102,103,104,105 In patients with myocardial infarction, increases in plasma α₁-AGP concentration are associated with increased lidocaine binding and increased total plasma concentrations of the drug, but only small increases in plasma concentration of free drug; these changes in α₁-AGP concentration and lidocaine binding are believed to account in part for accumulation of the drug observed in patients with myocardial infarction receiving prolonged infusions.103,104,105

Lidocaine readily crosses the blood-brain barrier and the placenta. Lidocaine also is distributed into milk; in one lactating woman, milk lidocaine concentration was approximately 40% of the serum concentration (from a sample obtained 2 hours earlier).117

Elimination

Lidocaine has an initial half-life of 7-30 minutes and a terminal half-life of 1.5-2 hours. In healthy individuals, the elimination half-lives of the active metabolites, monoethylglycinexylidide (MEGX) and glycinexylidide (GX) are 2 hours and 10 hours, respectively. In patients with myocardial infarction (with or without cardiac failure), the half-lives of lidocaine and MEGX have been reported to be prolonged; the half-life of GX is reportedly prolonged in patients with cardiac failure secondary to myocardial infarction. The half-life of lidocaine is reportedly also prolonged in patients with congestive heart failure or liver disease and may be prolonged following continuous IV infusions lasting longer than 24 hours. MEGX elimination may also be decreased in patients with congestive heart failure.

Approximately 90% of a parenteral dose of lidocaine is rapidly metabolized in the liver by de-ethylation to form MEGX and GX followed by cleavage of the amide bond to form xylidine and 4-hydroxyxylidine which are excreted in urine. Less than 10% of a dose is excreted unchanged in urine. MEGX and GX are pharmacologically active and may also cause CNS toxicity in some patients. The rate of metabolism of lidocaine appears to be limited by hepatic blood flow which may be reduced in patients after acute myocardial infarction and/or with congestive heart failure. Patients with congestive heart failure excrete more of a dose of lidocaine as unchanged drug and MEGX and less as GX and 4-hydroxyxylidine than do those without congestive heart failure. The rate of lidocaine metabolism may also be decreased in patients with liver disease, possibly because of altered perfusion in the liver or hepatic tissue necrosis. Distribution and elimination of lidocaine and MEGX appear to remain normal in patients with renal failure, but GX may accumulate in these patients when lidocaine is administered IV for several days.

Chemistry and Stability

Stability

Lidocaine hydrochloride injections and commercially available solutions of the drug in 5% dextrose should be stored at 25°C but may be exposed to temperatures up to 40°C; the injection and solutions should not be frozen, and the solutions should be protected from excessive heat. Commercially available solutions of lidocaine hydrochloride in 5% dextrose usually are stable for 18 months after the date of manufacture. Commercially available solutions of lidocaine hydrochloride in 5% dextrose may be provided in plastic containers. The amount of water that can permeate from the container into the overwrap is insufficient to significantly affect the injection. Solutions in contact with the plastic can leach out some of the chemical components in very small amounts; however, safety of the plastic has been confirmed in tests in animals according to USP biological tests for plastic containers.

At concentrations of 1-4 mg/mL in 5% dextrose injection, extemporaneously prepared lidocaine hydrochloride solutions appear to be stable at room temperature for at least 24 hours.

Lidocaine hydrochloride injection is compatible with most commercially available IV infusion fluids, but the pH of the drug may adversely affect additives such as dopamine, epinephrine, norepinephrine, or isoproterenol that require low pH for stability. If such admixtures are prepared, they should be administered shortly after preparation. Specialized references should be consulted for specific compatibility information. The manufacturers state that the commercially available solutions of lidocaine hydrochloride in 5% dextrose should not be mixed with other drugs.

Additional Information

The American Society of Health-System Pharmacists, Inc. represents that the information provided in the accompanying monograph was formulated with a reasonable standard of care, and in conformity with professional standards in the field. Readers are advised that decisions regarding use of drugs are complex medical decisions requiring the independent, informed decision of an appropriate health care professional, and that the information contained in the monograph is provided for informational purposes only. The manufacturer's labeling should be consulted for more detailed information. The American Society of Health-System Pharmacists, Inc. does not endorse or recommend the use of any drug. The information contained in the monograph is not a substitute for medical care.

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