TETRACAINE HYDROCHLORIDE
Clinical safety rating: caution
Comprehensive clinical and safety monograph for TETRACAINE HYDROCHLORIDE (TETRACAINE HYDROCHLORIDE).
Tetracaine hydrochloride is a local anesthetic of the ester type that reversibly blocks nerve conduction by decreasing sodium ion permeability across the neuronal membrane, thereby stabilizing the membrane and preventing the initiation and transmission of nerve impulses.
| Metabolism | Metabolized primarily by plasma pseudocholinesterases via hydrolysis to para-aminobenzoic acid (PABA) and diethylaminoethanol. |
| Excretion | Primarily metabolized by plasma pseudocholinesterase; renal excretion of metabolites accounts for >95% of elimination, with <2% excreted unchanged in urine. Biliary/fecal elimination is negligible. |
| Half-life | Terminal elimination half-life is approximately 1.5–3 minutes in plasma due to rapid hydrolysis; clinical effect duration is dose-dependent (15–30 minutes for topical anesthesia). |
| Protein binding | Approximately 75–80% bound to plasma proteins, primarily albumin and alpha-1-acid glycoprotein. |
| Volume of Distribution | Vd ~1.0–1.5 L/kg, indicating extensive tissue distribution; typical total Vd ~70 L in a 70 kg adult. |
| Bioavailability | Systemic bioavailability after topical application is minimal due to rapid local metabolism; oral bioavailability is negligible due to first-pass hydrolysis. For epidural/intrathecal, bioavailability is essentially 100% at the site of action. |
| Onset of Action | Topical (ophthalmic): 30–60 seconds; topical (mucosal): 1–3 minutes; epidural: 5–10 minutes; intrathecal: immediate to 5 minutes. |
| Duration of Action | Topical (ophthalmic): 15–30 minutes; topical (mucosal): 30–60 minutes; epidural: 1.5–3 hours; intrathecal: 1–2 hours; prolonged with epinephrine. |
| Molecular Weight | 300.82 |
Topical: 0.5-2% solution or ointment applied to affected area up to 4 times daily as needed. Maximum single dose: 20 mL of 2% solution (400 mg). Spinal anesthesia: 0.5% solution, 2-3 mL (10-15 mg) injected intrathecally.
| Dosage form | SOLUTION |
| Renal impairment | No specific dose adjustment recommended; tetracaine is metabolized primarily by plasma esterases and hepatic microsomal enzymes, with minimal renal excretion. Use 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 25-50% and monitor for toxicity. Child-Pugh Class C: Avoid use or use with extreme caution; consider alternative agents due to reduced metabolism. |
| Pediatric use | Topical: Apply sparingly to limited areas; not recommended for infants <1 year. For children >1 year, maximum application area: 10% body surface area. Dose per application: 0.1-0.2 mL/kg of 1% solution; maximum total dose: 4 mg/kg. Avoid repeated use. |
| Geriatric use | Reduce dose by 25-50% due to decreased hepatic esterase activity and reduced protein binding. Use lower concentrations (e.g., 0.5% instead of 1-2%) and limit application area. Monitor for prolonged effects and systemic toxicity. |
| 1st trimester | Limited data; avoid use due to potential fetal bradycardia and CNS effects. Case reports of fetal methemoglobinemia with ester anesthetics. Sufficient alternative agents available. |
| 2nd trimester | Use only if clearly needed; monitor fetal heart rate. Risk of maternal hypotension leading to uteroplacental insufficiency. |
| 3rd trimester | Use during labor may cause fetal bradycardia and neonatal respiratory depression. Avoid paracervical block in obstetrics. |
Clinical note
Comprehensive clinical and safety monograph for TETRACAINE HYDROCHLORIDE (TETRACAINE HYDROCHLORIDE).
| Placental transfer | Tetracaine crosses the placenta rapidly by passive diffusion due to its lipophilic nature; fetal plasma concentrations reach approximately 30-50% of maternal levels within minutes. Metabolized by pseudocholinesterase; fetal liver and plasma have low esterase activity, prolonging fetal exposure. |
| Breastfeeding |
■ FDA Black Box Warning
Risk of cardiac arrest and death when used for spinal anesthesia in doses exceeding recommended maximum; avoid use in patients with preexisting cardiovascular conditions.
| Serious Effects |
Known hypersensitivity to tetracaine or other ester-type local anesthetics (e.g., procaine, benzocaine)Severe hypotension or cardiogenic shockComplete heart block or uncontrolled bradyarrhythmiaMyasthenia gravisPlasma pseudocholinesterase deficiencyApplication to infected or denuded skin (risk of systemic toxicity)
| Precautions | Risk of anaphylaxis in patients with hypersensitivity to ester-type anesthetics or PABA-containing products, Severe hypotension and bradycardia during spinal anesthesia, Neurologic toxicity, including cauda equina syndrome, with high doses or intrathecal administration, Use with caution in patients with hepatic impairment, renal impairment, or cardiac disease, Avoid in myasthenia gravis due to potential for prolonged neuromuscular blockade |
| Food/Dietary | No clinically significant food interactions. Tetracaine is a topical/local anesthetic and systemic absorption is minimal when used as directed. Avoid alcohol consumption after application to large areas, as it may increase absorption or side effects. |
Loading safety data…
| Tetracaine is a short-acting ester with minimal systemic absorption following topical or regional use. Breastfeeding can continue after a washout period of at least 4 hours post-administration. No reports of adverse effects in infants. Consider timing feeds to coincide with next dose interval. |
| Lactation Rating | L2 - Moderately Safe (Hale's classification) |
| Teratogenic Risk | Tetracaine hydrochloride is a local anesthetic of the ester class. Animal studies are insufficient, and there are no adequate human studies in pregnant women. Systemic absorption is minimal with topical or regional use, but high-dose systemic exposure could potentially cause fetal bradycardia or CNS depression. The drug is not known to be teratogenic; risk is likely low when used as indicated. First trimester: theoretical risk from systemic toxicity, but no documented teratogenicity. Second trimester: safe for regional anesthesia with proper dosing. Third trimester: avoid high doses near delivery due to potential neonatal CNS and cardiac effects. |
| Fetal Monitoring | Monitor maternal vital signs (heart rate, blood pressure, respiratory rate) during administration. Observe for signs of systemic toxicity (metallic taste, tinnitus, perioral numbness, convulsions). Fetal heart rate monitoring is recommended if used during labor (e.g., epidural) to detect bradycardia. For topical use, no specific monitoring required beyond standard clinical observation. |
| Fertility Effects | No studies on human fertility. Animal studies do not indicate impaired fertility. Tetracaine is not expected to affect fertility in males or females at clinical doses. High systemic doses could theoretically cause transient ovarian or testicular dysfunction, but no evidence exists. |
| Clinical Pearls | Monitor for signs of systemic toxicity (CNS stimulation then depression, cardiovascular collapse) especially with application to mucous membranes or broken skin. Limit total dose; maximum recommended dose for topical anesthesia is 20 mg (1% solution) for adults. Avoid use in patients with known hypersensitivity to ester-type anesthetics. Tetracaine is rapidly absorbed through mucous membranes; apply with caution to avoid excessive systemic absorption. |
| Patient Advice | Avoid getting this medication in your eyes. · Do not apply to large areas of skin or to broken skin unless directed by a doctor. · Seek emergency medical help if you have signs of an allergic reaction: hives, difficulty breathing, swelling of your face, lips, tongue, or throat. · Notify your doctor if you experience dizziness, drowsiness, confusion, blurred vision, ringing in your ears, or unusual sensations. · This medication is for external use only; do not swallow it. |