LIDOCAINE VISCOUS
Clinical safety rating: safe
Beta-blockers may increase the risk of lidocaine toxicity Can cause CNS toxicity (seizures) and cardiovascular collapse.
Lidocaine is an amide-type local anesthetic that blocks voltage-gated sodium channels (Nav1.7, Nav1.8) in neuronal membranes, inhibiting depolarization and propagation of action potentials, thereby producing local anesthesia. It also has antiarrhythmic properties (class IB) by blocking sodium channels in cardiac myocytes.
| Metabolism | Hepatic metabolism primarily via CYP1A2 and CYP3A4 to monoethylglycinexylidide (MEGX) and glycinexylidide (GX); 90% undergoes dealkylation; less than 10% excreted unchanged in urine. |
| Excretion | Renal excretion of unchanged drug and metabolites accounts for >90% of elimination; <10% biliary/fecal. Metabolites include monoethylglycinexylidide (MEGX) and glycinexylidide (GX). |
| Half-life | Terminal elimination half-life is 1.5–2 hours (up to 3 hours in hepatic impairment). Clinically, redistribution half-life (~6 min) determines duration of action after short infusions. |
| Protein binding | 70–80% bound to alpha-1-acid glycoprotein (AAG) and albumin. Binding saturable and variable in disease states. |
| Volume of Distribution | Vd ~0.7–1.5 L/kg. Rapid distribution to highly perfused tissues (brain, heart), followed by slower equilibration with muscle and fat. |
| Bioavailability | Oral/topical: ~35% (due to extensive first-pass hepatic metabolism). Rectal: higher but variable (up to 50%). |
| Onset of Action | Oral/topical: 1–5 minutes for local anesthesia. |
| Duration of Action | 30–60 minutes for topical anesthesia. Prolonged in inflamed tissue or with co-administered vasoconstrictors. Systemic toxicity may persist longer. |
15 mL (300 mg) orally every 3 hours as needed for pain; maximum 8 doses per 24 hours.
| Dosage form | SOLUTION |
| Renal impairment | eGFR ≥15 mL/min: No adjustment. eGFR <15 mL/min: Use with caution; reduce dose or increase interval; avoid prolonged use. |
| Liver impairment | Child-Pugh A or B: Reduce total daily dose by 50%. Child-Pugh C: Contraindicated due to risk of systemic toxicity. |
| Pediatric use | Weight-based: 1-2 mg/kg per dose (max 4.5 mg/kg total per day) orally, applied topically to oral mucosa; not for systemic use in neonates. |
| Geriatric use | Initiate at low end of adult dosing (e.g., 15 mL every 6-8 hours), monitor for CNS side effects and arrhythmias; consider reduced clearance. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Beta-blockers may increase the risk of lidocaine toxicity Can cause CNS toxicity (seizures) and cardiovascular collapse.
| FDA category | Animal |
| Breastfeeding | Lidocaine is excreted into breast milk in low concentrations. M/P ratio is approximately 0.4. With typical viscous doses, infant exposure is minimal and unlikely to cause adverse effects. However, caution is advised with prolonged high-dose use; observe infant for sedation or poor feeding. |
| Teratogenic Risk |
■ FDA Black Box Warning
Not available (no FDA boxed warning for lidocaine viscous). However, lidocaine solutions >2% or inappropriately high doses can cause systemic toxicity, including cardiac arrest and death.
| Common Effects | ventricular arrhythmias |
| Serious Effects |
["Hypersensitivity to lidocaine or amide-type local anesthetics","Septicemia or severe trauma to the application site","Third-degree atrioventricular block (with no pacemaker) (for systemic use; topical use may still carry risk via absorption)","Use in premature neonates (due to increased risk of systemic toxicity)"]
| Precautions | ["Do not exceed recommended dose; excessive dosing can lead to systemic toxicity, including CNS excitation/depression and cardiac arrhythmias.","Use with caution in patients with hepatic impairment, congestive heart failure, or severe bradycardia.","Avoid use in patients with septicemia or severe trauma to mucosa.","May cause methemoglobinemia when used with other oxidizing agents (e.g., benzocaine)."] |
Loading safety data…
| Lidocaine crosses the placenta. First trimester: No well-documented teratogenicity in humans; animal studies show no fetal harm at clinically relevant doses. Second/third trimester: Risk of fetal bradycardia, central nervous system depression, and acidosis with high maternal doses or inadvertent intravascular administration. Avoid paracervical block for obstetric anesthesia due to potential fetal acidosis. |
| Fetal Monitoring | Maternal: Monitor for signs of systemic toxicity (perioral numbness, tinnitus, metallic taste, seizures, arrhythmias). Fetal: Continuous fetal heart rate monitoring during labor if used for analgesia; assess fetal heart rate variability for bradycardia. |
| Fertility Effects | No known adverse effects on fertility in humans. Animal studies show no impairment of fertility at clinical doses. |