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. |
| Molecular Weight | 234.34 |
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 | Generally considered safe; avoid high doses or repeated use. Animal studies show no evidence of teratogenicity. |
| 2nd trimester | Safe in recommended doses; monitor for maternal hypotension. |
| 3rd trimester | Safe at recommended doses; risk of fetal bradycardia if high maternal levels occur. |
Clinical note
Comprehensive clinical and safety monograph for XYLOCAINE 4% PRESERVATIVE FREE (XYLOCAINE 4% PRESERVATIVE FREE).
| Placental transfer | Lidocaine crosses placenta via passive diffusion; fetal/maternal ratio ~0.5–0.7. |
| Breastfeeding | Minimal excretion into breast milk; unlikely to affect infant. Use lowest effective dose. |
| Lactation Rating |
■ FDA Black Box Warning
Not applicable; lidocaine does not carry an FDA boxed warning in this formulation.
| Serious Effects |
Hypersensitivity to lidocaine or amide-type anestheticsSevere heart blockKnown history of porphyria
| 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 |
| Food/Dietary | No known food interactions. However, caution is advised when consuming hot foods or beverages while oral numbness persists to prevent burns. |
Loading safety data…
| L1 (Compatible) |
| 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). |
| 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. |
| Clinical Pearls | Xylocaine 4% preservative-free is indicated for local anesthesia via infiltration, nerve block, or topical application. Its maximum recommended dose is 4.5 mg/kg (or 300 mg total) in adults. Avoid use in patients with known hypersensitivity to amide anesthetics. For epidural anesthesia, use only the preservative-free formulation to prevent neurotoxicity. Monitor for signs of systemic toxicity (e.g., perioral numbness, metallic taste, seizures) due to accidental intravascular injection. |
| Patient Advice | Avoid eating or drinking until numbness resolves after oral or pharyngeal application to prevent injury. · Do not apply to large areas of broken skin or open wounds without medical supervision. · Inform your doctor if you have liver disease, heart conditions, or are pregnant. · Do not exceed the prescribed dose or frequency. · Seek immediate medical attention if you experience difficulty breathing, swelling, or severe dizziness. |