XYLOCAINE
Clinical safety rating: caution
Comprehensive clinical and safety monograph for XYLOCAINE (XYLOCAINE).
Lidocaine binds to and inhibits voltage-gated sodium channels in the neuronal membrane, stabilizing the membrane and preventing the initiation and conduction of nerve impulses, thereby producing local anesthesia.
| Metabolism | Primarily hepatic via CYP1A2 and CYP3A4 to active metabolites (monoethylglycinexylidide and glycinexylidide). |
| Excretion | Hepatic metabolism (primarily by CYP1A2 and CYP3A4) to metabolites, mainly monoethylglycinexylidide (MEGX) and glycinexylidide (GX); less than 10% excreted unchanged in urine. Renal excretion of metabolites: MEGX (70-80%) and GX (10-20%). Biliary/fecal elimination is minimal. |
| Half-life | Terminal elimination half-life is approximately 1.5 to 2 hours in adults, prolonged to 2-3 hours in patients with hepatic impairment, and may exceed 5 hours in neonates or patients with heart failure. |
| Protein binding | Approximately 65-70% bound to plasma proteins, primarily alpha-1-acid glycoprotein (AAG) and, to a lesser extent, albumin. |
| Volume of Distribution | Volume of distribution (Vd) is 0.8-1.3 L/kg. Higher Vd in neonates (up to 2.75 L/kg) indicates extensive tissue distribution. |
| Bioavailability | Intravenous: 100%; Intramuscular: 70-90%; Epidural: near 100%; Topical: variable and low due to systemic absorption, typically <10%; Oral: less than 30% due to extensive first-pass metabolism. |
| Onset of Action | Intravenous: 45-90 seconds; Intramuscular (injectable): 5-15 minutes; Topical (mucous membrane): 2-5 minutes; Epidural: 10-15 minutes. |
| Duration of Action | Intravenous: 10-20 minutes (anesthetic effect); Infiltration: 0.5-2 hours (dependent on epinephrine co-administration); Epidural: 1-2 hours. Duration is prolonged with addition of epinephrine. |
| Molecular Weight | 234.34 |
| Action Class | Local anaesthetic (Amides) |
| Brand Substitutes | Resocaine 2% Injection, Biocaine 2% Injection, Ligopil 2% Injection, Anescaine 2% Injection, Xylonumb 2% Injection, Lox 5% Ointment, Lidovac Ointment, Xylo Ointment, Gesicain Ointment, Xylo 4% Injection, Lox 4% Injection, Oculan 1% Injection, Lignox 1% Injection, Ocu Ligno 1% Injection, Xylocaine Heavy 5% Injection, Lox Heavy 5% Injection, Xynova 5% Injection, Anescaine 5% Injection |
1-5 mg/kg (max 300 mg) local infiltration; epidural: 1-2% solution, 5-20 mL.
| Dosage form | OINTMENT |
| Renal impairment | No adjustment required for GFR >30 mL/min; avoid in severe renal impairment (GFR <30 mL/min) due to risk of accumulation. |
| Liver impairment | Child-Pugh A/B: reduce dose by 50%; Child-Pugh C: contraindicated. |
| Pediatric use | 1-2 mg/kg (max 4.5 mg/kg) local infiltration; adjust based on lean body weight. |
| Geriatric use | Reduce dose by 40-50% due to decreased clearance and increased sensitivity to CNS/cardiac effects. |
| 1st trimester | Limited human data; avoid unless clearly needed. Animal studies have shown no teratogenicity at clinically relevant doses. |
| 2nd trimester | Use caution; consider benefits vs risks. No known fetal harm in standard doses. |
| 3rd trimester | Use with caution near term; may cause fetal bradycardia or CNS depression if high doses or paracervical block used. |
Clinical note
Comprehensive clinical and safety monograph for XYLOCAINE (XYLOCAINE).
| Placental transfer | Crosses placenta rapidly via passive diffusion; fetal plasma levels about 50-60% of maternal levels. |
| Breastfeeding | Excreted into breast milk in small amounts; unlikely to cause adverse effects in infant. Use lowest effective dose, monitor infant for CNS depression or irritability. |
■ FDA Black Box Warning
None.
| Serious Effects |
Hypersensitivity to lidocaine or amide-type anestheticsSevere heart block (including 2nd or 3rd degree AV block without pacemaker)Severe hypotensionSepsis at injection siteMucosal administration with inflamed/infected tissue (increased absorption)
| Precautions | Risk of local anesthetic systemic toxicity (LAST) including CNS and cardiovascular effects, especially with inadvertent intravascular injection or high doses, Use with caution in patients with hepatic impairment, severe renal impairment, or hypovolemia, May cause methemoglobinemia, especially in infants, Monitor ECG when used intravenously for arrhythmias |
| Food/Dietary | No clinically significant food interactions reported. |
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| Lactation Rating |
| L2 (Safer) |
| Teratogenic Risk | First trimester: No increased risk of major malformations observed in human studies. Second and third trimesters: Potential for fetal bradycardia and central nervous system depression with high maternal serum levels. Use only if clearly needed. |
| Fetal Monitoring | Continuous fetal heart rate monitoring during continuous infusion or high-dose administration. Monitor maternal vital signs, ECG, and neurological status for toxicity. |
| Fertility Effects | No evidence of impaired fertility in animal studies. Clinical data on human fertility effects are lacking; unlikely to cause reproductive impairment at therapeutic doses. |
| Clinical Pearls | Use minimum effective dose to avoid systemic toxicity; maximum dose without epinephrine is 4.5 mg/kg (not to exceed 300 mg), with epinephrine (1:200,000) is 7 mg/kg (not to exceed 500 mg). Rapid absorption from highly vascular areas (e.g., intercostal blocks) increases toxicity risk. Always aspirate before injection to prevent intravascular administration. Mixing with epinephrine prolongs duration and reduces peak plasma levels. For pediatric patients, calculate dose based on weight and use reduced concentrations (0.5-1%). In patients with hepatic impairment, reduce dose due to decreased metabolism. Concurrent use with CYP1A2 inhibitors (e.g., fluvoxamine) may increase lidocaine levels. |
| Patient Advice | Avoid driving or operating machinery until numbness and effects have completely worn off. · Do not eat or drink until sensation returns to prevent biting your tongue or cheek. · Report any signs of allergic reaction (rash, difficulty breathing, swelling) to your healthcare provider immediately. · If you experience dizziness, blurred vision, ringing in ears, or metallic taste, seek emergency care. · Inform your doctor about all medications you take, especially heart medications, anticoagulants, or other local anesthetics. · Numbness and lack of sensation are normal during the procedure; do not scratch or rub the numbed area. |