XYLOCAINE 4% PRESERVATIVE FREE
Clinical safety rating: caution
Comprehensive clinical and safety monograph for XYLOCAINE 4% PRESERVATIVE FREE (XYLOCAINE 4% PRESERVATIVE FREE).
Lidocaine stabilizes the neuronal membrane by inhibiting sodium ion influx through voltage-gated sodium channels, thereby blocking the initiation and propagation of action potentials, resulting in local anesthesia.
| Metabolism | Lidocaine is primarily metabolized in the liver via oxidative N-dealkylation (CYP1A2 and CYP3A4) to monoethylglycinexylidide (MEGX) and glycinexylidide (GX), which have reduced pharmacological activity. |
| Excretion | Renal: ~90% as metabolites (mostly 4-hydroxy-2,6-xylidine and conjugates); <10% unchanged. Biliary/fecal: minor. |
| Half-life | Terminal elimination half-life: ~1.5–2 hours (adults). Prolonged in hepatic impairment, congestive heart failure, or neonates. |
| Protein binding | ~65% bound to alpha-1-acid glycoprotein (AAG) and albumin. Binding varies with concentration and AAG levels. |
| Volume of Distribution | Vd: ~1.0–1.5 L/kg (adults). Higher in neonates (~2.5 L/kg). Reflects rapid distribution to highly perfused tissues. |
| Bioavailability | Oral: negligible (extensive first-pass metabolism). Topical: minimally absorbed via intact skin; via mucous membranes, absorption is rapid and dose-dependent. Intravenous: 100%. |
| Onset of Action | Topical (mucous membranes): 2–5 minutes; Infiltration: 0.5–2 minutes; Epidural: 5–15 minutes; Intravenous: 45–90 seconds. |
| Duration of Action | Infiltration: 0.5–2 hours (with epinephrine up to 2–6 hours); Epidural: 1–3 hours; Topical: 15–45 minutes. |
Maximum 4.5 mg/kg (not to exceed 300 mg) via subcutaneous infiltration, epidural, or nerve block; repeat dosing after 30 minutes if needed.
| Dosage form | INJECTABLE |
| Renal impairment | No specific dose adjustment recommended; use with caution in severe renal impairment (eGFR <30 mL/min) due to potential accumulation of metabolites. |
| Liver impairment | Contraindicated in Child-Pugh class C; for Child-Pugh class A or B, reduce dose by 50% and monitor for toxicity. |
| Pediatric use | Maximum 4.5 mg/kg via infiltration or nerve block; for neonates, reduce to 3 mg/kg. Repeat dosing interval: every 30–60 minutes as needed. |
| Geriatric use | Reduce dose by 20–30% in patients >65 years; monitor for prolonged effect and adverse reactions. Maximum single dose: 200 mg. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for XYLOCAINE 4% PRESERVATIVE FREE (XYLOCAINE 4% PRESERVATIVE FREE).
| Breastfeeding | Excreted into breast milk in small amounts (M/P ratio ~0.4-1.0). Relative infant dose ~1-4% of maternal weight-adjusted dose. Generally considered compatible with breastfeeding; observe infant for drowsiness or feeding difficulties. |
| Teratogenic Risk | Lidocaine is not teratogenic in animals. Human data: no increased risk of major congenital malformations. First trimester: limited data, generally considered low risk. Second/third trimester: no known fetal harm with standard doses; high doses may cause fetal bradycardia or CNS depression. Avoid paracervical block in first trimester due to potential fetal acidosis. Category B (FDA). |
■ FDA Black Box Warning
Not applicable; lidocaine does not carry an FDA boxed warning in this formulation.
| Serious Effects |
["Severe hypotension","Complete heart block or other severe conduction abnormalities","Known hypersensitivity to lidocaine or amide-type local anesthetics","Myasthenia gravis (relative contraindication according to some sources)","Use in patients with porphyria (theoretical risk)"]
| Precautions | ["Excessive dosage or rapid absorption can cause systemic toxicity (CNS stimulation/depression, cardiovascular collapse)","Use with caution in patients with severe liver disease, hypovolemia, heart block, or impaired cardiac conduction","Monitor for signs of toxicity (perioral numbness, tinnitus, seizures) during administration","Avoid injection into infected or inflamed tissues due to reduced efficacy and increased absorption risk"] |
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| Fetal Monitoring | ECG monitoring for maternal cardiac effects (dysrhythmias) with high doses. Fetal heart rate monitoring to detect bradycardia during paracervical or epidural use. Monitor for signs of systemic toxicity (perioral numbness, tinnitus, convulsions). |
| Fertility Effects | No evidence of impaired fertility in animal studies. In humans, no adverse effects on fertility reported with standard use. |