XYLOCAINE VISCOUS
Clinical safety rating: caution
Comprehensive clinical and safety monograph for XYLOCAINE VISCOUS (XYLOCAINE VISCOUS).
Lidocaine is an amide-type local anesthetic that blocks voltage-gated sodium channels, inhibiting nerve impulse propagation and reducing pain sensation.
| Metabolism | Primarily metabolized in the liver by CYP3A4 and CYP1A2 to monoethylglycinexylidide (MEGX) and glycinexylidide (GX); further hydrolysis to xylidine and other metabolites. |
| Excretion | Renal excretion of metabolites: ~90%. Unchanged drug: <10%. Biliary/fecal: minor. |
| Half-life | Terminal elimination half-life: 1.5-2 hours in adults; prolonged in hepatic impairment or heart failure (up to 6-8 hours). In neonates, half-life may be 3-6 hours due to immature metabolism. |
| Protein binding | 55-65% bound to alpha-1-acid glycoprotein (AAG) and albumin; binding decreases in neonates and inflammatory states. |
| Volume of Distribution | Vd: 0.7-1.5 L/kg. Higher in neonates (1.5-4.5 L/kg) due to increased body fat and reduced protein binding. |
| Bioavailability | Oral (viscous): ~35% (extensive first-pass metabolism). Topical mucosal: variable, but significant systemic absorption can occur with large doses. |
| Onset of Action | Topical (oral mucosa): 1-5 minutes. Oral (viscous solution): 1-5 minutes. Not for injectable use. |
| Duration of Action | Topical/oral mucosal: 15-30 minutes (anesthetic effect). Systemic absorption may prolong effects; caution with large doses. |
| Molecular Weight | 234.34 |
| Action Class | Local anaesthetic (Amides) |
Adults: 5-15 mL orally (or swish and spit) 4-6 times daily, not to exceed 4 doses in 12 hours or 30 mL in 12 hours.
| Dosage form | SOLUTION |
| Renal impairment | No specific GFR-based dose adjustment recommended; caution in severe renal impairment due to potential accumulation of metabolites. |
| Liver impairment | Child-Pugh Class A/B: No adjustment; Class C: Reduce dose by 50% (e.g., max 15 mL/12h) due to reduced lidocaine clearance. |
| Pediatric use | Neonates and infants: 1.5-4 mg/kg (max 4.5 mg/kg/24h) orally every 4-6 hours; Children: 2-3 mL orally every 3-4 hours, not to exceed 4 doses in 12 hours. |
| Geriatric use | Initiate at lower end of dosing range (e.g., 5 mL orally) and titrate cautiously due to increased sensitivity and potential for toxicity. |
| 1st trimester | Lidocaine crosses the placenta. Available data do not suggest an increased risk of major birth defects. However, use only if clearly needed. |
| 2nd trimester | Lidocaine crosses the placenta. No evidence of fetal harm in animal studies; limited human data. Use only if clearly needed. |
| 3rd trimester | Lidocaine crosses the placenta. Use near term may cause neonatal CNS depression and bradycardia. Avoid excessive doses and prolonged use. |
Clinical note
Comprehensive clinical and safety monograph for XYLOCAINE VISCOUS (XYLOCAINE VISCOUS).
| Placental transfer | Lidocaine crosses the placenta by passive diffusion. Fetal/maternal ratio approximately 0.5-0.6. Unbound drug rapidly equilibrates. |
| Breastfeeding | Lidocaine is excreted into breast milk in small amounts, with relative infant dose estimated at 0.5-2% of maternal weight-adjusted dose. No adverse effects reported in infants. Caution with repeated high doses or when the infant is premature or has hepatic impairment. |
■ FDA Black Box Warning
Not for injection or ophthalmic use. Do not use for teething. Severe adverse reactions including seizures, cardiac arrest, and death have occurred with improper use, especially in children.
| Serious Effects |
Hypersensitivity to lidocaine or amide-type anestheticsSevere atrioventricular block (without pacemaker)Acute congestive heart failure (class III-IV)Hypovolemia or shockMarked hypotensionIn patients with known severe hepatic disease (due to impaired metabolism)
| Precautions | Risk of methemoglobinemia, especially in patients with G6PD deficiency or other predisposing factors; avoid excessive dosage due to risk of systemic toxicity; use with caution in patients with hepatic impairment, severe trauma, or mucosal ulceration. |
| Food/Dietary | Avoid food and drink for at least 1 hour after application due to risk of aspiration and burns from hot foods/liquids. No known drug-food interactions. |
Loading safety data…
| Lactation Rating | L2 (Probably Compatible) |
| Teratogenic Risk | Lidocaine (XYLOCAINE VISCOUS) is classified as FDA Pregnancy Category B. Animal studies do not indicate fetal harm, but adequate human studies in pregnant women are lacking. First trimester: No known teratogenic risk; however, use only if clearly needed. Second and third trimesters: No specific fetal risks reported; however, placental transfer occurs. Use during labor and delivery may affect uterine contractions and fetal heart rate; avoid excessive doses. |
| Fetal Monitoring | Monitor maternal vital signs (heart rate, blood pressure, respiratory rate) and central nervous system status during administration. Fetal heart rate monitoring is recommended if used during labor. Observe for signs of lidocaine toxicity (e.g., seizures, arrhythmias) in both mother and fetus/infant. No specific laboratory monitoring required. |
| Fertility Effects | No human data on fertility effects. Animal studies have not shown impaired fertility at clinically relevant doses. However, high doses may affect reproductive performance in animal models. Advise patients with fertility concerns that no significant impact is expected with therapeutic use. |
| Clinical Pearls | Xylocaine Viscous (lidocaine 2% viscous solution) is primarily used for topical anesthesia of the oropharyngeal mucosa. Avoid excessive dosing to prevent systemic toxicity, especially in children and elderly patients. Do not use for teething pain in infants due to risk of methemoglobinemia and airway compromise. Maximum single dose: 4.5 mg/kg; do not administer more frequently than every 3 hours. Observe for signs of CNS toxicity (perioral numbness, dizziness, slurred speech) and cardiovascular depression. Use with caution in patients with severe hepatic disease or pseudocholinesterase deficiency. |
| Patient Advice | Do not eat or drink for at least 1 hour after application to prevent choking or aspiration due to numbing effect. · Swish and hold the solution in the mouth for 2-5 minutes, then spit out. Do not swallow. · Use the smallest amount necessary to control symptoms. Do not use more often than every 3 hours. · Contact your doctor immediately if you experience difficulty breathing, severe dizziness, or slow heartbeat. · Keep out of reach of children. Accidental ingestion can cause serious side effects. · Do not use for teething pain in infants or young children due to risk of serious side effects. |