Get your patient on Lidocaine Hydrochloride - Lidocaine Hydrochloride solution (Lidocaine Hydrochloride)

• Lidocaine Hydrochloride Injection, USP is not recommended for intrathecal use.
• Avoid use of Lidocaine Hydrochloride Injection, USP solutions containing antimicrobial preservatives (i.e., multiple-dose vials) for epidural or caudal anesthesia [see Warnings and Precautions (5.3 )] .
• Discard unused portions of solution not containing preservatives, i.e., those supplied in single-dose vials, following initial use.
• Visually inspect this product for particulate matter and discoloration prior to administration whenever solution and container permit. Lidocaine Hydrochloride Injection, USP are clear, colorless solutions. Do not administer solutions which are discolored or contain particulate matter.
• Parenteral drug products should be inspected visually for particulate matter and discoloration prior to administration whenever the solution and container permit. Solutions which are discolored (e.g., pinkish or darker than slightly yellow) or which contain particulate matter or precipitate should not be administered.
• Mixing or the prior or intercurrent use of any other local anesthetic with Lidocaine Hydrochloride Injection, USP is not recommended because of insufficient data on the clinical use of such mixtures.

Administration Precautions

• Lidocaine Hydrochloride Injection, USP is to be administered in carefully adjusted dosages by or under the supervision of experienced clinicians who are well versed in the diagnosis and management of dose-related toxicity and other acute emergencies which might arise from the block to be employed.
• Use Lidocaine Hydrochloride Injection, USP only if the following are immediately available: oxygen, cardiopulmonary resuscitative equipment and drugs, and the personnel resources needed for proper management of toxic reactions and related emergencies [see Warnings and Precautions (5.1 ), Adverse Reactions (6 ), Overdosage (10 )].
• The toxic effects of local anesthetics are additive. Monitor for neurologic and cardiovascular effects related to local anesthetic systemic toxicity when additional local anesthetics are administered with Lidocaine Hydrochloride Injection, USP [see Warnings and Precautions (5.1 ), Drug Interactions (7.1 ), Overdosage (10 ) ].
• Aspirate for blood or cerebrospinal fluid (where applicable) prior to injecting Lidocaine Hydrochloride Injection, USP, both the initial dose and all subsequent doses, to avoid intravascular or intrathecal injection. However, a negative aspiration for blood or cerebrospinal fluid does not ensure against an intravascular or intrathecal injection [see Warnings and Precautions (5.7 )] .
• Avoid rapid injection of a large volume of Lidocaine Hydrochloride Injection, USP and use fractional (incremental) doses when feasible.
• During major regional nerve blocks, such as those of the brachial plexus or lower extremity, the patient should have an indwelling intravenous catheter to assure adequate intravenous access. The lowest dosage of Lidocaine Hydrochloride Injection, USP that results in effective anesthesia should be used to avoid high plasma levels and serious adverse reactions.
• Perform careful and constant monitoring of cardiovascular and respiratory (adequacy of oxygenation and ventilation) vital signs and the patient’s level of consciousness after each local anesthetic injection.
• Use Lidocaine Hydrochloride Injection, USP in carefully restricted quantities in areas of the body supplied by end arteries or having otherwise compromised blood supply such as digits, nose, external ear, or penis [see Warnings and Precautions (5.10 )] .

The dosage of Lidocaine Hydrochloride Injection, USP administered varies with the anesthetic procedure, the area to be anesthetized, the vascularity of the tissues, the number of neuronal segments to be blocked, the depth of anesthesia and degree of muscle relaxation required, the duration of anesthesia desired, individual tolerance, and the physical condition of the patient. Administer the smallest dosage and concentration required to produce the desired result.

The types of block and recommended Lidocaine Hydrochloride Injection, USP concentrations are shown in Table 1. The dosages suggested in this table are for normal healthy adults and refer to the use of epinephrine-free solutions. Consider administration of solutions containing epinephrine when large volumes are required.

•Dose determined by number of dermatomes to be anesthetized (2 to 3 mL/dermatome).

•• Dose should not exceed 4 mg/kg.

The above suggested concentrations and volumes serve only as a guide. Other volumes and concentrations may be used provided the total maximum recommended dose is not exceeded [see Dosage and Administration (2.5 )] .

These recommended doses serve only as a guide to the amount of local anesthetic required for most indicated procedures. The actual volumes and concentrations to be used depend on a number of factors such as type and extent of surgical procedure, depth of anesthesia and degree of muscular relaxation required, duration of anesthesia required, and the physical condition of the patient. In all cases, the lowest concentration and smallest dose that will produce the desired result should be given. The maximum dosage limit within the recommended dosage range must be individualized in each case after evaluating the size and physical status of the patient, as well as the anticipated rate of systemic absorption from a particular injection site.

During epidural administration, administer Lidocaine Hydrochloride Injection, USP, 1% (10 mg/mL), and 2% (20 mg/mL) solutions in incremental doses of 3 mL to 5 mL with sufficient time between doses to detect toxic manifestations of unintentional intravascular or intrathecal injection. Administer injections slowly, with frequent aspirations before and during the injection to avoid intravascular injection. Perform syringe aspirations before and during each supplemental injection in continuous (intermittent) catheter techniques. Repeat doses of Lidocaine Hydrochloride Injection, USP should be preceded by a test dose containing epinephrine if not clinically contraindicated. Use only the single-dose vials for caudal or epidural anesthesia; avoid use of the multiple-dose vials for these procedures, which contain a preservative [see Dosage and Administration (2.1 , 2.4 ), Warnings and Precautions (5.7 )] .

In the event of the known injection of a large volume of local anesthetic solution into the subarachnoid space, after suitable resuscitation and if the catheter is in place, consider attempting the recovery of drug by draining a moderate amount of cerebrospinal fluid (such as 10 mL) through the epidural catheter.

Three mL of Lidocaine HCl and Epinephrine Injection without antimicrobial preservative (1.5% lidocaine with 1:200,000 epinephrine) is recommended for use as a test dose prior to caudal and lumbar epidural blocks when clinical conditions permit. This test dose may serve as a warning of unintended intravascular or intrathecal injection. Closely monitor for early clinical signs of toxicity following each test dose [see Warnings and Precautions (5.7 )] . Allot adequate time for onset of spinal block to detect possible intrathecal injection. An intravascular or intrathecal injection is still possible even if results of the test dose are negative. The test dose itself may produce a systemic toxic reaction, high spinal, or cardiovascular effects from the epinephrine [see Warnings and Precautions (5.1 ), Overdosage (10 )] .

Lidocaine Hydrochloride Injection, USP solutions containing epinephrine or other vasoconstrictors should not be used for this technique. Proper use of the double tourniquet technique is essential in the performance of intravenous regional anesthesia.

For intravenous regional anesthesia, the dose administered should not exceed 4 mg/kg in adults.

Adults

For normal healthy adults, the individual maximum recommended dose of lidocaine hydrochloride with epinephrine should not exceed 7 mg/kg of body weight, and in general it is recommended that the maximum total dose not exceed 500 mg. When used without epinephrine, the maximum individual dose should not exceed 4.5 mg/kg of body weight, and in general it is recommended that the maximum total dose does not exceed 300 mg. For continuous epidural or caudal anesthesia, the maximum recommended dosage should not be administered at intervals of less than 90 minutes. When continuous lumbar or caudal epidural anesthesia is used for non-obstetrical procedures, a higher total dose may be administered if required to produce adequate anesthesia.

The maximum recommended dose per 90 minute period of lidocaine hydrochloride for paracervical block in obstetrical patients and non-obstetrical patients is 200 mg total. One half of the total dose is usually administered to each side. Inject slowly, five minutes between sides [see Pregnancy (8.1 )] .

Pediatric Patients

A maximum dose of Lidocaine Hydrochloride Injection, USP for children varies based on age and weight. For children over 3 years of age with a normal lean body mass and normal body development, the maximum dose is determined by the child’s age and weight. For example, in a child of 5 years weighing approximately 23 kg, the dose of lidocaine hydrochloride should not exceed approximately 75 mg to 100 mg (3.3 mg/kg to 4.4 mg/kg). The use of dilute solutions (i.e., 0.25% to 0.5%) and total dosages not to exceed 3 mg/kg are recommended for induction of intravenous regional anesthesia in children.

The lowest effective concentration and lowest effective dose should be used. Dilution of available concentrations with 0.9% sodium chloride injection may be required to obtain the required final concentration.

Risk Summary

Available published data and decades of clinical use with Lidocaine Hydrochloride Injection, USP in pregnant women have not identified any drug- associated risk for major birth defects, miscarriage, or other adverse maternal or fetal outcomes. Local anesthetics may cause varying degrees of toxicity to the mother and fetus and adverse reactions include alterations of the central nervous system, peripheral vascular tone and cardiac function (see Clinical Considerations) .

In a published animal reproduction study, pregnant rats administered lidocaine by continuous subcutaneous infusion at a dose approximately 9.6 times the maximum recommended human dose (MRHD) of 500 mg in Lidocaine Hydrochloride Injection, USP during the period of organogenesis resulted in lower fetal body weights [see Data] .

The estimated background risk of major birth defects and miscarriage for the indicated population is unknown. All pregnancies have a background risk of birth defects, loss, or other adverse outcomes. In the United States general population, the estimated background risks of major birth defects and miscarriage in clinically recognized pregnancies is 2% to 4% and 15%to 20%, respectively.

Clinical Considerations

Maternal Adverse Reactions

Maternal hypotension has resulted from regional anesthesia. Local anesthetics produce vasodilation by blocking sympathetic nerves. Therefore, during treatment of systemic toxicity, maternal hypotension or fetal bradycardia following regional block, the parturient should be maintained in the left lateral decubitus position if possible or manual displacement of the uterus off the great vessels be accomplished. Elevating the patient’s legs will also help prevent decreases in blood pressure. The fetal heart rate also should be monitored continuously, and electronic fetal monitoring is highly advisable.

Labor or delivery

Local anesthetics rapidly cross the placenta, and when used for epidural, paracervical, pudendal or caudal block anesthesia, can cause varying degrees of maternal, fetal and neonatal toxicity [see Clinical Pharmacology (12.3)] . The incidence and degree of toxicity depend upon the procedure performed, the type and amount of drug used, and the technique of drug administration. Adverse reactions in the parturient, fetus and neonate involve alterations of the central nervous system, peripheral vascular tone and cardiac function. However, dosage recommendations for spinal anesthesia are much lower than dosage recommendations for other major blocks.

Spinal anesthesia may alter the forces of parturition through changes in uterine contractility or maternal expulsive efforts. Spinal anesthesia has also been reported to prolong the second stage of labor by removing the parturient’s reflex urge to bear down or by interfering with motor function. The use of obstetrical anesthesia may increase the need for forceps assistance. The use of some local anesthetic drug products during labor and delivery may be followed by diminished muscle strength and tone for the first day or two of life.

Data

Animal Data

Reproduction studies have been performed in rats at doses up to 6.6 times the human dose and have revealed no evidence of harm to the fetus caused by lidocaine hydrochloride.

In a published study, lidocaine administered to pregnant rats by continuous subcutaneous infusion during the period of organogenesis at 100, 250, and 500 mg/kg/day, did not produce any structural abnormalities, but did result in lower fetal weights at 500 mg/kg/day dose (approximately 9.6 times the maximum recommended human dose [MRHD] of 500 mg lidocaine on a mg/m2 basis) in the absence of maternal toxicity.

Risk Summary

Published data report the presence of lidocaine and its metabolites in human milk in low amounts, along with poor oral bioavailability. There are no data on the effect of lidocaine on the breastfed infant or the effect on milk production. The developmental and health benefits of breastfeeding should be considered along with the mother’s clinical need for Lidocaine Hydrochloride Injection, USP and any potential adverse effects on the breastfed child from Lidocaine Hydrochloride Injection, USP or from the underlying maternal condition.

Dosages in children should be reduced, commensurate with age, body weight and physical condition [see Dosage and Administration (2.6 )] .

Elderly patients should be given reduced doses commensurate with their age and physical condition [see Dosage and Administration (2.6 )] .

Amide-type local anesthetics such as lidocaine are metabolized by the liver. Patients with severe hepatic impairment, because of their inability to metabolize local anesthetics normally, are at greater risk of developing toxic plasma concentrations and potentially local anesthetic systemic toxicity. Therefore, consider reduced dosing and increased monitoring for local anesthetic systemic toxicity in patients with hepatic impairment treated with Lidocaine Hydrochloride Injection with epinephrine, especially with repeat doses [see Warnings and Precautions (5.8 )] .

The safety and effectiveness of Lidocaine Hydrochloride Injection, USP depend on proper dosage, correct technique, adequate precautions, and readiness for emergencies. Careful and constant monitoring of cardiovascular and respiratory (adequacy of ventilation) vital signs and the patient’s state of consciousness should be performed after injection of Lidocaine Hydrochloride Injection, USP solutions.

Possible early warning signs of central nervous system (CNS) toxicity are restlessness, anxiety, incoherent speech, lightheadedness, numbness and tingling of the mouth and lips, metallic taste, tinnitus, dizziness, blurred vision, tremors, twitching, CNS depression, or drowsiness. Delay in proper management of dose-related toxicity, underventilation from any cause, and/or altered sensitivity may lead to the development of acidosis, cardiac arrest, and possibly, death.

During major regional nerve blocks, such as those of the brachial plexus or lower extremity, the patient should have an indwelling intravenous catheter to assure adequate intravenous access. Use the lowest dosage of Lidocaine Hydrochloride Injection, USP that results in effective anesthesia to avoid high plasma levels and serious adverse effects. Avoid rapid injection of a large volume of Lidocaine Hydrochloride Injection, USP solution and administer fractional (incremental) doses when feasible.

Injection of repeated doses of Lidocaine Hydrochloride Injection, USP may cause significant increases in plasma levels with each repeated dose due to slow accumulation of the drug or its metabolites, or to slow metabolic degradation. Tolerance to elevated blood levels varies with the status of the patient. Debilitated, elderly patients and acutely ill patients should be given reduced doses commensurate with their age and physical status.

Cases of methemoglobinemia have been reported in association with local anesthetic use. Although all patients are at risk for methemoglobinemia, patients with glucose-6-phosphate dehydrogenase deficiency, congenital or idiopathic methemoglobinemia, cardiac or pulmonary compromise, infants under 6 months of age, and concurrent exposure to oxidizing agents or their metabolites are more susceptible to developing clinical manifestations of the condition [see Drug Interactions (7.5 )] . If local anesthetics must be used in these patients, close monitoring for symptoms and signs of methemoglobinemia is recommended.

Signs of methemoglobinemia may occur immediately or may be delayed some hours after exposure and are characterized by a cyanotic skin discoloration and abnormal coloration of the blood. Methemoglobin levels may continue to rise; therefore, immediate treatment is required to avert more serious central nervous system and cardiovascular adverse effects, including seizures, coma, arrhythmias, and death. Discontinue Lidocaine Hydrochloride Injection, USP and any other oxidizing agents. Depending on the severity of the symptoms, patients may respond to supportive care, i.e., oxygen therapy, hydration. More severe symptoms may require treatment with methylene blue, exchange transfusion, or hyperbaric oxygen.

Avoid use of Lidocaine Hydrochloride Injection, USP solutions containing antimicrobial preservatives (i.e., those supplied in multiple-dose vials) for epidural or caudal anesthesia because safety has not been established with such use.

Intra-articular infusions of local anesthetics following arthroscopic and other surgical procedures is an unapproved use, and there have been post-marketing reports of chondrolysis in patients receiving such infusions. The majority of reported cases of chondrolysis have involved the shoulder joint; cases of gleno-humeral chondrolysis have been described in pediatric and adult patients following intra-articular infusions of local anesthetics with and without epinephrine for periods of 48 to 72 hours. There is insufficient information to determine whether shorter infusion periods are not associated with these findings. The time of onset of symptoms, such as joint pain, stiffness and loss of motion can be variable, but may begin as early as the 2nd month after surgery. Currently, there is no effective treatment for chondrolysis; patients who experienced chondrolysis have required additional diagnostic and therapeutic procedures and some required arthroplasty or shoulder replacement.

Risk of Severe, Persistent Hypertension Due to Drug Interactions Between Lidocaine Hydrochloride Injection with Epinephrine and Monoamine Oxidase Inhibitors and Tricyclic Antidepressants

Administration of Lidocaine Hydrochloride Injection with Epinephrine in patients receiving monoamine oxidase inhibitors (MAOI), or tricyclic antidepressants may result in severe, prolonged hypertension. Concurrent use of these agents should generally be avoided. In situations when concurrent therapy is necessary, careful monitoring of the patient's hemodynamic status is essential [see Drug Interactions (7.2 )] .

Risk of Severe, Persistent Hypertension or Cerebrovascular Accidents Due to Drug Interactions Between Lidocaine Hydrochloride Injection with Epinephrine and Ergot-Type Oxytocic Drugs

Concurrent administration of Lidocaine Hydrochloride Injection with Epinephrine and ergot-type oxytocic drugs may cause severe, persistent hypertension or cerebrovascular accidents. Avoid use of Lidocaine Hydrochloride Injection with Epinephrine concomitantly with ergot-type oxytocic drugs [see Drug Interactions (7.3 )] .

Risk of Hypertension and Bradycardia Due to Drug Interactions Between Lidocaine Hydrochloride Injection with Epinephrine and Nonselective Beta-Adrenergic Antagonists

Administration of Lidocaine Hydrochloride Injection with Epinephrine in patients receiving nonselective beta-adrenergic antagonists may cause severe hypertension and bradycardia. Concurrent use of these agents should generally be avoided. In situations when concurrent therapy is necessary, careful monitoring of the patient's blood pressure and heart rate is essential [see Drug Interactions (7.4 )].

Lidocaine Hydrochloride Injection with epinephrine solutions contain sodium metabisulfite, a sulfite that may cause allergic-type reactions including anaphylactic symptoms and life-threatening or less severe asthmatic episodes in certain susceptible people. The overall prevalence of sulfite sensitivity in the general population is unknown and probably low. Sulfite sensitivity is seen more frequently in asthmatic than in non-asthmatic people. Lidocaine Hydrochloride Injection without epinephrine does not contain sodium metabisulfite.

Anaphylactic reactions may occur following administration of lidocaine hydrochloride [see Adverse Reactions (6 )] . Lidocaine hydrochloride should be used with caution in persons with known drug sensitivities. Patients allergic to para-aminobenzoic acid derivatives (procaine, tetracaine, benzocaine, etc.) have not shown cross-sensitivity to lidocaine hydrochloride.

Unintended intravascular or intrathecal injection of Lidocaine Hydrochloride Injection, USP may be associated with systemic toxicities, including CNS or cardiorespiratory depression and coma, progressing ultimately to respiratory arrest. Unintentional intrathecal injection during the intended performance of caudal or lumbar epidural block or nerve blocks near the vertebral column has resulted in underventilation or apnea (“Total or High Spinal”). A high spinal has been characterized by paralysis of the legs, loss of consciousness, respiratory paralysis, and bradycardia [see Adverse Reactions (6 )] .

Aspirate for blood or cerebrospinal fluid (where applicable) before injecting Lidocaine Hydrochloride Injection, USP, both the initial dose and all subsequent doses, to avoid intravascular or intrathecal injection. However, a negative aspiration for blood or cerebrospinal fluid does not ensure against an intravascular or intrathecal injection

.

Use of Test Dose with Epidural Anesthesia

To serve as a warning of unintended intravascular or intrathecal injection, 3 mL of Lidocaine HCl and Epinephrine Injection without antimicrobial preservative (1.5% lidocaine with 1:200,000 epinephrine) may be used as a test dose prior to administration of the full dose in caudal and lumbar epidural blocks [see Dosage and Administration (2.4 )] . Three mL of Lidocaine HCl and Epinephrine Injection (1.5% lidocaine with 1:200,000 epinephrine) without antimicrobial preservative contains 45 mg lidocaine and 15 mcg epinephrine. An intravascular or intrathecal injection is still possible even if results of the test dose are negative.

Signs/symptoms of unintended intravascular or intrathecal injection of the test dose of Lidocaine HCl and Epinephrine Injection and monitoring recommendations are described below.

• Unintended intravascular injection: Likely to produce a transient “epinephrine response” within 45 seconds, consisting of an increase in heart rate and/or systolic blood pressure, circumoral pallor, palpitations, and nervousness in the unsedated patient. The sedated patient may exhibit only a pulse rate increase of 20 or more beats per minute for 15 or more seconds. Therefore, following the test dose, the heart rate should be monitored for increases. Patients on beta- blockers may not manifest changes in heart rate, but blood pressure monitoring can detect a transient rise in systolic blood pressure.
• Unintended intrathecal injection: Evidenced within a few minutes by signs of spinal block (e.g., decreased sensation of the buttocks, paresis of the legs, or, in the sedated patient, absent knee jerk).

The test dose itself may produce a systemic toxic reaction, high spinal or epinephrine-induced cardiovascular effects [see Overdosage (10 )] .

Because amide local anesthetics such as lidocaine are metabolized by the liver, consider reduced dosing and increased monitoring for lidocaine systemic toxicity in patients with moderate to severe hepatic impairment who are treated with Lidocaine Hydrochloride Injection, USP, especially with repeat doses [see Use in Specific Populations (8.6 )] .

Lidocaine Hydrochloride Injection, USP should also be given in reduced doses in patients with impaired cardiovascular function since they may be less able to compensate for functional changes associated with the prolongation of A-V conduction produced by these drugs. Monitor patients closely for blood pressure, heart rate, and ECG changes.

Use Lidocaine Hydrochloride Injection, USP with Epinephrine in carefully restricted quantities in areas of the body supplied by end arteries or having otherwise compromised blood supply, such as digits, nose, external ear, or penis. Patients with peripheral vascular disease and those with hypertensive vascular disease may exhibit exaggerated vasoconstrictor response. Ischemic injury or necrosis may result.

Serious dose-related cardiac arrhythmias may occur if preparations containing a vasoconstrictor such as epinephrine (e.g., Lidocaine Hydrochloride Injection, USP with Epinephrine) are used in patients during or following the administration of potent inhalation anesthetics [see Drug Interactions (7.6 )] . In deciding whether to concurrently use Lidocaine Hydrochloride Injection, USP with Epinephrine with potent inhalation anesthetics in the same patient, the combined action of both agents upon the myocardium, the concentration and volume of vasoconstrictor used, and the time since injection, when applicable, should be taken into account.

Small doses of local anesthetics (e.g., Lidocaine Hydrochloride Injection, USP) injected into the head and neck area, including retrobulbar, dental and stellate ganglion blocks, may produce adverse reactions similar to systemic toxicity seen with unintentional intravascular injections of larger doses. The injection procedures require the utmost care. Confusion, convulsions, respiratory depression and/or respiratory arrest, and cardiovascular stimulation or depression have been reported. These reactions may be due to intra- arterial injection of the local anesthetic with retrograde flow to the cerebral circulation. They may also be due to puncture of the dural sheath of the optic nerve during retrobulbar block with diffusion of any local anesthetic along the subdural space to the midbrain. Monitor circulation and respiration and constantly observe patients receiving Lidocaine Hydrochloride Injection, USP blocks. Resuscitative equipment and drugs, and personnel for treating adverse reactions should be immediately available. Dosage recommendations should not be exceeded [see Dosage and Administration (2.2 )] .

Many drugs used during the conduct of anesthesia are considered potential triggering agents for familial malignant hyperthermia. Since it is not known whether amide-type local anesthetics may trigger this reaction and since the need for supplemental general anesthesia cannot be predicted in advance, it is suggested that a standard protocol for the management of malignant hyperthermia should be available. Early unexplained signs of tachycardia, tachypnea, labile blood pressure and metabolic acidosis may precede temperature elevation. Successful outcome is dependent on early diagnosis, prompt discontinuance of the suspect triggering agent(s) and institution of treatment, including oxygen therapy, indicated supportive measures and dantrolene (consult dantrolene sodium intravenous package insert before using).

Clinicians who perform retrobulbar blocks should be aware that there have been reports of respiratory arrest following local anesthetic injection. Prior to retrobulbar block (e.g., with Lidocaine Hydrochloride Injection, USP with epinephrine), as with all other regional procedures, resuscitative equipment and drugs, and personnel to manage respiratory arrest or depression, convulsions, and cardiac stimulation or depression should be immediately available [see Warnings and Precautions (5.14 )] . As with other anesthetic procedures, patients should be constantly monitored following ophthalmic blocks for signs of these adverse reactions, which may occur following relatively low total doses.

Because of the long duration of anesthesia, when Lidocaine Hydrochloride Injection, USP with epinephrine [0.5% (5 mg/mL) of lidocaine] is used for dental injections, warn patients about the possibility of inadvertent trauma to tongue, lips, and buccal mucosa and advise them not to chew solid foods until sensation returns [see Patient Counseling Information (17 )].

The intramuscular injection of lidocaine HCl may result in an increase in creatine phosphokinase levels. Thus, the use of this enzyme determination, without isoenzyme separation, as a diagnostic test for the presence of acute myocardial infarction may be compromised by the intramuscular injection of lidocaine HCl.

The toxic effects of local anesthetics are additive. If coadministration of other local anesthetics with Lidocaine Hydrochloride Injection, USP cannot be avoided, monitor patients for neurologic and cardiovascular effects related to local anesthetic systemic toxicity [see Warnings and Precautions (5.1 )] .

The administration of Lidocaine Hydrochloride Injection, USP with Epinephrine to patients receiving monoamine oxidase inhibitors or tricyclic antidepressants may produce severe, prolonged hypertension. Concurrent use of these agents should generally be avoided. In situation when concurrent therapy is necessary, careful monitoring of the patient’s hemodynamic status is essential [see Warnings and Precautions (5.5 )] .

Concurrent administration of vasopressor drugs (for the treatment of hypotension related to obstetric blocks) and ergot-type oxytocic drugs may cause severe, persistent hypertension or cerebrovascular accidents. Avoid use of Lidocaine Hydrochloride Injection, USP with Epinephrine concomitantly with ergot-type oxytocic drugs [see Warnings and Precautions (5.5 )] .

Administration of Lidocaine Hydrochloride Injection, USP with Epinephrine in patients receiving nonselective beta-adrenergic antagonists may cause severe hypertension and bradycardia. Concurrent use of these agents should generally be avoided. In situations when concurrent therapy is necessary, careful monitoring of the patient's blood pressure and heart rate is essential [see Warnings and Precautions (5.5 )] .

Patients that are administered local anesthetics may be at increased risk of developing methemoglobinemia when concurrently exposed to the following oxidizing agents:

Serious dose-related cardiac arrhythmias may occur if preparations containing epinephrine (e.g., Lidocaine Hydrochloride Injection, USP with Epinephrine) are used in patients during or following the administration of potent inhalation anesthetics [see Warnings and Precautions (5.11 )] .

Phenothiazines and butyrophenones may reduce or reverse the pressor effect of epinephrine. Concurrent use of Lidocaine Hydrochloride Injection, USP with Epinephrine and these agents should generally be avoided. In situation when concurrent therapy is necessary, careful patient monitoring is essential.

Lidocaine hydrochloride stabilizes the neuronal membrane by inhibiting the ionic fluxes required for the initiation and conduction of impulses thereby effecting local anesthetic action.

Excessive blood levels may cause changes in cardiac output, total peripheral resistance, and mean arterial pressure. With central neural blockade these changes may be attributable to block of autonomic fibers, a direct depressant effect of the local anesthetic agent on various components of the cardiovascular system, and/or the beta-adrenergic receptor stimulating action of epinephrine when present. The net effect is normally a modest hypotension when the recommended dosages are not exceeded.

Factors such as acidosis and the use of CNS stimulants and depressants affect the CNS levels of lidocaine hydrochloride required to produce overt systemic effects. Objective adverse manifestations become increasingly apparent with increasing venous plasma levels above 6 mcg free base per mL.

Systemic plasma levels of lidocaine following administration of Lidocaine Hydrochloride Injection, USP do not correlate with local efficacy.

Absorption

Information derived from diverse formulations, concentrations and usages reveals that lidocaine hydrochloride is completely absorbed following parenteral administration, its rate of absorption depending, for example, upon various factors such as the site of administration and the presence or absence of a vasoconstrictor agent. Except for intravascular administration, the highest blood levels are obtained following intercostal nerve block and the lowest after subcutaneous administration.

Distribution

The plasma binding of lidocaine hydrochloride is dependent on drug concentration, and the fraction bound decreases with increasing concentration. At concentrations of 1 to 4 mcg of free base per mL 60 to 80 percent of lidocaine hydrochloride is protein bound. Binding is also dependent on the plasma concentration of the alpha-1-acid glycoprotein.

Lidocaine hydrochloride crosses the blood-brain and placental barriers, presumably by passive diffusion.

Elimination

The elimination half-life of lidocaine hydrochloride following an intravenous bolus injection is typically 1.5 to 2 hours.

Metabolism

Lidocaine hydrochloride is metabolized rapidly by the liver, and biotransformation includes oxidative N-dealkylation, ring hydroxylation, cleavage of the amide linkage, and conjugation. N-dealkylation, a major pathway of biotransformation, yields the metabolites monoethylglycinexylidide and glycinexylidide. The pharmacological/toxicological actions of these metabolites are similar to, but less potent than, those of lidocaine hydrochloride.

Excretion

Approximately 90% of lidocaine hydrochloride administered is excreted in the form of various metabolites, and less than 10% is excreted unchanged by the kidneys. The primary metabolite in urine is a conjugate of 4-hydroxy-2,6-dimethylaniline.

Specific Populations

Patients with Hepatic Impairment

Because of the rapid rate at which lidocaine hydrochloride is metabolized, any condition that affects liver function may alter lidocaine HCl kinetics. The half-life may be prolonged two-fold or more in patients with liver dysfunction.

Patients with Renal Impairment

Renal dysfunction does not affect lidocaine hydrochloride kinetics but may increase the accumulation of metabolites.

Carcinogenesis

Studies of lidocaine hydrochloride in animals to evaluate the carcinogenic potential have not been conducted.

Mutagenesis

Studies of lidocaine hydrochloride in animals to evaluate the mutagenic potential have not been conducted.

Impairment of Fertility

In a published study, female Sprague-Dawley rats were treated subcutaneously with lidocaine via osmotic pumps starting two weeks prior to mating, and reproductive effects were assessed. Rats dosed up to the high dose of 500 mg/kg/day (approximately 45 times the MRDD on a mg/m2 basis) showed no effects on copulatory rate, pregnancy rate, numbers of corpora lutea, or implantations.