LIDOCAINE
Clinical safety rating: safe
Animal studies have demonstrated safety
Lidocaine is a sodium channel blocker that inhibits the influx of sodium ions into cardiac Purkinje fibers and myocytes, thereby stabilizing the neuronal membrane and decreasing automaticity. It also exhibits local anesthetic effects by reversibly binding to voltage-gated sodium channels in nerve cell membranes, blocking impulse conduction.
| Metabolism | Lidocaine is primarily metabolized in the liver via deethylation to monoethylglycinexylidide (MEGX) and then to glycinexylidide (GX) by cytochrome P450 enzymes, mainly CYP1A2 and CYP3A4. Hepatic clearance is dependent on hepatic blood flow. |
| Excretion | Renal excretion of metabolites: 4-hydroxyxylidine (70-80% renal, 10-20% biliary/fecal), unchanged lidocaine <10% renal. Total renal elimination ~90% (as metabolites), biliary/fecal ~10%. |
| Half-life | Terminal elimination half-life 1.5-2 hours (normal hepatic function). In CHF or hepatic impairment, prolonged to 6-8 hours; in neonates, 3-6 hours. Context: rapid redistribution after IV bolus (alpha half-life ~8 min) accounts for brief clinical effect, while terminal half-life determines accumulation with infusion. |
| Protein binding | ~70% bound primarily to alpha-1-acid glycoprotein (AAG), also to albumin. Binding is concentration-dependent and saturable; increased AAG in acute phase (e.g., MI, surgery) reduces free fraction. |
| Volume of Distribution | Vd: 0.8-1.3 L/kg (adults), increased in neonates (1.5-4 L/kg). Clinical meaning: wide distribution reflects high tissue uptake, especially in well-perfused organs (brain, heart, lungs). Vd increases in CHF due to reduced cardiac output and perfusion. |
| Bioavailability | IV: 100%; Oral: <5% (extensive first-pass hepatic metabolism); IM: ~60-70% (variable); Epidural: complete systemic absorption (100% bioavailability into systemic circulation); Topical/transdermal: 3-10% (intact skin), ~20% (mucous membranes). |
| Onset of Action | IV: 45-90 seconds (antiarrhythmic); Epidural: 5-15 min; Spinal: immediate (<1 min); Peripheral nerve block: 4-17 min (depending on dose and technique); Topical: 2-5 min (mucous membranes), 30-60 min (intact skin with EMLA). |
| Duration of Action | IV antiarrhythmic: 10-20 min (single bolus); Epidural: 60-120 min (with epinephrine up to 200 min); Peripheral nerve block: 60-180 min (with epinephrine up to 300 min); Topical: 30-60 min. Duration prolonged in hepatic impairment. |
| Molecular Weight | 234.34 |
For ventricular arrhythmias: IV bolus 1-1.5 mg/kg, then continuous infusion 1-4 mg/min. For local anesthesia: 0.5-2% solution, max 4.5 mg/kg (300 mg) without epinephrine, 7 mg/kg (500 mg) with epinephrine.
| Dosage form | OINTMENT |
| Renal impairment | No dose adjustment required for GFR >10 mL/min. For GFR <10 mL/min: reduce dose by 25% or monitor for toxicity. Lidocaine is not significantly removed by hemodialysis. |
| Liver impairment | Child-Pugh Class A: no adjustment. Child-Pugh Class B: reduce dose by 50%. Child-Pugh Class C: reduce dose by 75% or avoid use; monitor levels. |
| Pediatric use | For local anesthesia: 0.5-2% solution, max 4.5 mg/kg (7 mg/kg with epinephrine). For ventricular arrhythmias: IV loading 1 mg/kg, then infusion 20-50 mcg/kg/min. |
| Geriatric use | Reduce doses due to decreased hepatic clearance and increased volume of distribution. Use lower loading doses (0.5-1 mg/kg) and lower infusion rates (1-2 mg/min). Monitor for CNS and cardiac toxicity. |
| 1st trimester | Lidocaine is generally considered safe in the first trimester; use only if clearly needed. Animal studies have not shown teratogenicity, but adequate human studies are limited. |
| 2nd trimester | No documented adverse effects on fetus; used commonly for local anesthesia during pregnancy. |
| 3rd trimester | Use with caution near term due to potential for neonatal depression if high doses are administered; rapid placental transfer possible. |
Clinical note
Beta-blockers may increase the risk of lidocaine toxicity Can cause CNS toxicity (seizures) and cardiovascular collapse.
| Placental transfer | Readily crosses the placenta by passive diffusion; peak fetal levels within 30 minutes of maternal administration. |
| Breastfeeding | Lidocaine is excreted into breast milk in small amounts; minimal risk to infant at typical doses. Monitor for signs of adverse effects such as irritability or drowsiness. |
■ FDA Black Box Warning
Lidocaine injection is not indicated for the treatment of atrial fibrillation or atrial flutter with rapid ventricular response, or for prophylaxis of ventricular arrhythmias in acute myocardial infarction. Continuous intra-arterial administration is contraindicated. Risk of severe cardiac toxicity, including asystole, with high doses or rapid infusion.
| Common Effects | ventricular arrhythmias |
| Serious Effects |
History of hypersensitivity to lidocaine or amide-type anestheticsSevere heart block (without pacemaker)Stokes-Adams syndromeWolff-Parkinson-White syndrome
| Precautions | Monitor for signs of central nervous system (CNS) toxicity (e.g., drowsiness, paresthesias, seizures) and cardiac toxicity (e.g., bradycardia, hypotension, arrhythmias)., Use caution in patients with hepatic impairment, heart failure, or renal impairment., Risk of severe hypotension, bradycardia, and cardiac arrest with rapid intravenous administration., Lidocaine can cause respiratory depression and arrest if given in excessive doses., Use with caution in patients with hypovolemia, shock, or severe bradycardia. |
Loading safety data…
| Lactation Rating | L2 (Limited data - Probably compatible) |
| Teratogenic Risk | First trimester: Limited human data, not associated with major malformations. Second and third trimesters: Fetal bradycardia and central nervous system depression possible with high maternal doses. |
| Fetal Monitoring | Continuous fetal heart rate monitoring during paracervical block or intravenous use; maternal vital signs and ECG for signs of toxicity; assess for fetal bradycardia. |
| Fertility Effects | No evidence of adverse effects on male or female fertility in animal studies; human data lacking. |
| Food/Dietary | No significant food interactions. Grapefruit juice has minimal effect on lidocaine metabolism. Avoid alcohol due to additive CNS depression. Caffeine may theoretically increase risk of arrhythmias; avoid excessive consumption. |
| Clinical Pearls | Lidocaine is a class Ib antiarrhythmic and amide-type local anesthetic. For arrhythmias, use only for ventricular arrhythmias (especially post-MI) due to increased risk of asystole with atrial arrhythmias. Maximum single dose for local anesthesia: 4.5 mg/kg without epinephrine, 7 mg/kg with epinephrine. Toxic effects (CNS: perioral numbness, metallic taste, seizures; CV: hypotension, bradycardia, arrest) are dose-related. For IV use, bolus 1-1.5 mg/kg, then infusion at 1-4 mg/min. Reduce dose in heart failure, liver disease, elderly. Check for allergies to amide anesthetics (rare cross-reactivity with other amides). Use with caution with CYP1A2 inhibitors (e.g., fluvoxamine, ciprofloxacin) and antiarrhythmics (e.g., amiodarone, procainamide). |
| Patient Advice | Inform your healthcare provider if you have any history of heart disease, liver disease, or seizures before using lidocaine. · Do not exceed the prescribed dose or frequency of application; overuse can lead to serious side effects including irregular heartbeat, seizures, or breathing problems. · For topical use, avoid applying to large areas of skin, broken or irritated skin, or near eyes and mucous membranes. · Seek immediate medical help if you experience symptoms of toxicity such as blurred vision, ringing in ears, slurred speech, confusion, severe dizziness, or slow/irregular heartbeat. · Avoid consuming alcohol while using lidocaine, as it may increase the risk of side effects. · Do not drive or operate heavy machinery if you experience dizziness, drowsiness, or blurred vision after using lidocaine. |