XYLOCAINE 1.5% W/ DEXTROSE 7.5%
Clinical safety rating: caution
Comprehensive clinical and safety monograph for XYLOCAINE 1.5% W/ DEXTROSE 7.5% (XYLOCAINE 1.5% W/ DEXTROSE 7.5%).
Lidocaine is an amide-type local anesthetic that blocks sodium channels, thereby inhibiting the propagation of action potentials in peripheral nerves, leading to local anesthesia.
| Metabolism | Hepatic metabolism via CYP1A2 and CYP3A4, primarily to monoethylglycinexylidide (MEGX) and glycinexylidide (GX), which are less active. |
| Excretion | Renal excretion of metabolites (predominantly 4-hydroxy-2,6-xylidine and conjugates) accounts for >80% of elimination; less than 10% eliminated unchanged in urine. Biliary/fecal excretion of metabolites contributes <10%. |
| Half-life | Terminal elimination half-life: 1.5–2 hours in adults with normal hepatic function; may be prolonged to 3–5 hours in patients with hepatic impairment or congestive heart failure. |
| Protein binding | Approximately 65–75% bound primarily to alpha-1-acid glycoprotein (AAG) and to a lesser extent albumin. Binding is concentration-dependent and decreases at high concentrations. |
| Volume of Distribution | Vd: 0.8–1.3 L/kg. Represents extensive tissue distribution and rapid equilibration from plasma into well-perfused organs (brain, heart, liver, kidneys). Increased Vd in neonates and elderly. |
| Bioavailability | Epidural: near 100% (due to vascular absorption from epidural space); Absorption from injection site depends on vascularity and dose. Oral: negligible (<5%) due to extensive first-pass metabolism. |
| Onset of Action | Epidural: 5–15 minutes; Spinal: within 1–2 minutes; Peripheral nerve block: 5–15 minutes; Infiltration: 1–2 minutes. |
| Duration of Action | Epidural: 60–90 minutes of surgical anesthesia (time to regression of sensory level by 2 dermatomes); Spinal: 45–60 minutes of surgical anesthesia; Peripheral nerve block: 1–3 hours depending on dose and technique. Addition of epinephrine may prolong duration by 30–50%. |
| Molecular Weight | 234.34 |
Spinal anesthesia: 1.5-2 mL (22.5-30 mg lidocaine) for lower extremity or perineal procedures; 2-3 mL (30-45 mg) for lower abdominal or urological procedures. Administered via lumbar puncture.
| Dosage form | INJECTABLE |
| Renal impairment | No specific dose adjustment required for spinal administration; however, monitor for systemic toxicity in severe renal impairment (CrCl <30 mL/min). |
| Liver impairment | Child-Pugh Class A: no adjustment. Child-Pugh Class B/C: reduce dose by 50% and monitor for prolonged anesthesia and toxicity. |
| Pediatric use | Not FDA-approved for pediatric spinal anesthesia. Weight-based dosing for other routes of lidocaine: 1.5-2 mg/kg as a single spinal dose, administered by anesthesiologist. |
| Geriatric use | Reduce dose by 30-50% due to decreased CSF volume and prolonged neural blockade. Use low end of adult range (1.5-2 mL) and monitor for hypotension and bradycardia. |
| 1st trimester | Lidocaine crosses placenta. Use only if clearly needed; no well-controlled studies, but no evidence of teratogenicity in animal studies. |
| 2nd trimester | Same as T1. Use with caution; may cause fetal bradycardia if high concentrations reach fetus. |
| 3rd trimester | Use near term may cause neonatal CNS depression and bradycardia. Avoid excessive doses; use lowest effective dose. |
Clinical note
Comprehensive clinical and safety monograph for XYLOCAINE 1.5% W/ DEXTROSE 7.5% (XYLOCAINE 1.5% W/ DEXTROSE 7.5%).
| Placental transfer | Lidocaine crosses placenta via passive diffusion. Fetal/maternal ratio ranges 0.5-0.7. Bound to fetal tissues; clearance slower in neonate. |
| Breastfeeding | Lidocaine is excreted into breast milk in small amounts (milk:plasma ratio ~0.4). Oral bioavailability in infant is low. Consider risk of accumulation in preterm or ill infants. Generally compatible with breastfeeding. |
■ FDA Black Box Warning
Not all local anesthetics for infiltration or nerve block are approved for spinal anesthesia; this formulation is not approved for spinal anesthesia. Use only as directed.
| Common Effects | Allergic reaction Application site reactions burning irritation itching and redness |
| Serious Effects |
Hypersensitivity to lidocaine or amide-type anestheticsSevere heart block (unless paced)Severe hypotension or hypovolemiaMyasthenia gravis (relative, but listed as absolute in some sources)
| Precautions | Risk of systemic toxicity including CNS excitation/depression and cardiac depression; use with caution in patients with hepatic impairment, cardiac disease, or elderly. Avoid intravascular injection; monitor for signs of toxicity. Resuscitative equipment should be available. |
| Food/Dietary |
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| Lactation Rating | L2 (Probably Compatible) |
| Teratogenic Risk | Lidocaine is classified as FDA pregnancy category B. Animal studies have not demonstrated fetal risk, but no adequate human studies exist. There is no evidence of teratogenicity in humans when used at recommended doses. However, use in the first trimester should be based on necessity. In the second and third trimesters, lidocaine is generally considered safe, but caution is advised due to potential fetal bradycardia or central nervous system depression if high systemic levels occur. The dextrose component at 7.5% is not considered teratogenic. |
| Fetal Monitoring | Monitor maternal vital signs (heart rate, blood pressure, respiratory rate) and signs of systemic toxicity (dizziness, tinnitus, perioral numbness, seizures). Fetal heart rate monitoring is recommended during labor and delivery to detect bradycardia. Assess for signs of local anesthetic systemic toxicity (LAST) including central nervous system and cardiovascular effects. |
| Fertility Effects | Lidocaine has no known direct effects on human fertility. In animal studies, no impairment of fertility was observed at clinically relevant doses. However, the dextrose component at 7.5% may cause transient hyperglycemia but does not affect fertility. |
| No specific food interactions. However, avoid alcohol for at least 24 hours due to potential additive central nervous system depression. |
| Clinical Pearls | This is a hyperbaric (heavy) spinal anesthetic solution (density > CSF) used for unilateral or saddle block anesthesia. Position patient carefully: for saddle block, keep sitting for 3-5 min post-injection; for unilateral block, lateral decubitus with operative side down for 5-10 min. Baricity ensures predictable spread. Onset: 5-10 min. Duration: 1-2 hours. Use 0.5-1.5 mL (7.5-22.5 mg lidocaine). Beware of high spinal if dosage or positioning errs. Contraindicated in hemorrhagic shock, infection at injection site, increased ICP, and coagulopathy. |
| Patient Advice | You will receive numbing medicine into your lower back to block pain for surgery. · You may feel a cold sensation or transient tingling during injection. · You will be positioned carefully after the injection to control where the numbness goes. · Numbness typically lasts 1 to 2 hours; you may also have temporary weakness in your legs. · Do not drive or operate machinery for at least 24 hours after the procedure. · Report any persistent headache, back pain, or leg weakness to your doctor immediately. · Avoid alcohol and sedatives for 24 hours as they can increase side effects. |