LIDOCAINE HYDROCHLORIDE VISCOUS
Clinical safety rating: safe
Beta-blockers may increase the risk of lidocaine toxicity Can cause CNS toxicity (seizures) and cardiovascular collapse.
Lidocaine is a local anesthetic that stabilizes neuronal membranes by blocking voltage-gated sodium channels, thereby inhibiting the initiation and propagation of action potentials. It also has antiarrhythmic properties (Class Ib) by accelerating repolarization and reducing automaticity in cardiac tissues.
| Metabolism | Primarily hepatic via CYP1A2 and CYP3A4 to monoethylglycinexylidide and glycinexylidide; also conjugated to 4-hydroxy-2,6-dimethylaniline. |
| Excretion | Renal: ~90% as metabolites (mainly 4-hydroxy-2,6-xylidine and glucuronides), <10% unchanged. Biliary/fecal: minor (<5%). |
| Half-life | Terminal elimination half-life: 1.5–2 hours (adults); prolonged in heart failure (2.5–4 hours) or hepatic disease (up to 5–7 hours). Context: short t1/2 limits toxic accumulation with topical use. |
| Protein binding | ~70% bound to alpha-1-acid glycoprotein (AAG) and albumin; binding increases with AAG elevation (e.g., inflammation). |
| Volume of Distribution | 1.1–2.0 L/kg (adults). Clinical meaning: extensive distribution into well-perfused tissues, including brain and heart, contributing to potential CNS/cardiac toxicity. |
| Bioavailability | Viscous topical (oral mucosa): approximately 3–15% (highly variable due to swallowing and mucosal absorption; significant first-pass metabolism). Not bioavailable orally (IV form only for systemic use). |
| Onset of Action | Viscous topical (oral mucosa): 1–2 minutes; infiltration: 2–5 minutes; no parenteral IV formulation for viscous product. |
| Duration of Action | Viscous topical: 30–60 minutes (mucosal anesthesia); infiltration: 1–2 hours (with epinephrine). Viscous use indicated for pharyngeal anesthesia. |
| Molecular Weight | 288.81 |
Adult: 15 mL (300 mg) orally every 3 hours, not to exceed 8 doses in 24 hours. Viscous formulation swished and swallowed.
| Dosage form | SOLUTION |
| Renal impairment | No specific dose adjustment recommended; use with caution in severe renal impairment due to potential accumulation of metabolites. |
| Liver impairment | Child-Pugh Class A: No adjustment. Child-Pugh Class B: Reduce dose by 50%. Child-Pugh Class C: Avoid use or reduce dose by 75% with close monitoring. |
| Pediatric use | Weight-based: 4.5 mg/kg/dose (maximum 300 mg) orally every 3 hours as needed; not to exceed 4 doses in 12 hours. Safety in infants <6 months not established. |
| Geriatric use | Reduce initial dose by 25-50% due to decreased hepatic clearance; monitor for CNS toxicity and cardiac effects. |
| 1st trimester | Limited data; lidocaine crosses placenta. Use only if clearly needed. Avoid large doses or frequent administration due to potential for fetal bradycardia or CNS depression. |
| 2nd trimester | Similar to t1; no significant increase in malformations reported. Use lowest effective dose for shortest duration. |
| 3rd trimester | Risk of neonatal CNS depression, bradycardia, and apnea if administered near term. Use only if benefit outweighs risk. Monitor neonate for adverse effects. |
Clinical note
Beta-blockers may increase the risk of lidocaine toxicity Can cause CNS toxicity (seizures) and cardiovascular collapse.
| FDA category | Animal |
| Placental transfer | Rapidly crosses placenta; fetal concentration ~50-70% of maternal. Risk of fetal acidosis and bradycardia with high maternal doses or systemic toxicity. |
■ FDA Black Box Warning
Contains lidocaine, which can cause methemoglobinemia, particularly in neonates and infants. Use with extreme caution in patients with G6PD deficiency, or concurrent use of oxidizing agents. Risk of systemic toxicity (seizures, cardiac arrest) if absorbed in large amounts.
| Common Effects | ventricular arrhythmias |
| Serious Effects |
Hypersensitivity to lidocaine or any amide-type local anestheticsSevere heart block (sinoatrial, atrioventricular, or intraventricular) without pacemakerAdams-Stokes syndromeKnown history of malignant hyperthermiaSevere hypotension or cardiogenic shock
| Precautions | Systemic absorption can cause CNS stimulation/depression, cardiovascular depression, and methemoglobinemia. Use smallest effective amount. Avoid application to traumatized mucosa or open wounds. Monitor for signs of toxicity in young children and elderly. Discontinue if rash or irritation occurs. |
Loading safety data…
| Breastfeeding | Lidocaine is excreted into breast milk in low amounts (milk:plasma ratio ~0.4-0.6). Oral absorption by infant is minimal due to first-pass metabolism. No adverse effects reported in infants with maternal use. However, avoid direct application to nipples to prevent infant ingestion of high concentrations. |
| Lactation Rating | L2 (Compatible) based on Hale's classification; low risk to infant. |
| Teratogenic Risk | Lidocaine hydrochloride viscous is classified as FDA Pregnancy Category B. Animal reproduction studies have not demonstrated fetal risk, and there are no adequate and well-controlled studies in pregnant women. However, lidocaine can cross the placental barrier by passive diffusion. At term, fetal/maternal plasma concentration ratio is approximately 0.5-0.7. No teratogenic effects have been reported in humans when used appropriately. However, high systemic levels can cause fetal bradycardia and acidosis. Use during first trimester is generally considered low risk, but caution is advised. During second and third trimesters, risk remains low but monitor for maternal toxicity. |
| Fetal Monitoring | Maternal monitoring includes assessment for lidocaine toxicity (CNS effects like lightheadedness, perioral numbness, metallic taste, tinnitus; cardiovascular effects like hypotension, bradycardia). Fetal monitoring should include fetal heart rate assessment for bradycardia or late decelerations, particularly with high doses or prolonged use. If administered near term, monitor for neonatal depression (respiratory, CNS). No specific routine fetal monitoring is required for topical use, but systemic absorption should be minimized. |
| Fertility Effects | Lidocaine has no known direct effects on fertility in humans. Animal studies have not shown impaired fertility at clinically relevant doses. However, severe systemic toxicity could theoretically affect reproductive function, but at therapeutic topical doses, no impact on fertility is expected. |
| Food/Dietary |
| Avoid hot foods or beverages until sensation returns to prevent oral burns. No known direct food-drug interactions. |
| Clinical Pearls | Lidocaine viscous is a topical anesthetic for oral mucosal use. Avoid excessive volume to prevent systemic absorption and toxicity, especially in children. Use with caution in patients with hepatic impairment or heart block. Maximum dose: 4.5 mg/kg (not to exceed 300 mg). Do not apply to open wounds or ulcers. Swish and spit or swallow depending on indication; swallowing increases systemic exposure. |
| Patient Advice | Use only as directed; do not exceed recommended dose. · Do not eat or drink for at least 1 hour after use to prevent aspiration or burning the mouth. · You may experience temporary numbness or altered taste. · Seek emergency care if you experience dizziness, drowsiness, confusion, or seizures. · Store at room temperature, away from children. |