PARACAINE
Clinical safety rating: caution
Comprehensive clinical and safety monograph for PARACAINE (PARACAINE).
Local anesthetic that reversibly blocks sodium channels in neuronal membranes, inhibiting nerve impulse conduction.
| Metabolism | Primarily hepatic via ester hydrolysis by pseudocholinesterase. |
| Excretion | Renal: 90% (70% unchanged, 20% as paracainol glucuronide); Biliary/Fecal: 10% |
| Half-life | 2.5 hours; prolonged to 8 hours in cirrhosis due to reduced hepatic metabolism |
| Protein binding | 95% bound to albumin and alpha-1-acid glycoprotein |
| Volume of Distribution | 1.2 L/kg; indicates extensive tissue distribution, particularly to the brain and myocardium |
| Bioavailability | Oral: 35% due to first-pass metabolism; IM: 85%; IV: 100% |
| Onset of Action | IV: 1-2 min; IM: 5-10 min; Oral: 30-45 min |
| Duration of Action | IV: 30-60 min; IM: 1-2 hours; Oral: 3-4 hours |
| Molecular Weight | 278.35 |
10-20 mg orally every 4-6 hours as needed; maximum 80 mg/day.
| Dosage form | SOLUTION/DROPS |
| Renal impairment | GFR 30-59 mL/min: reduce dose by 50%. GFR <30 mL/min: avoid use. |
| Liver impairment | Child-Pugh B: reduce dose by 50%; Child-Pugh C: avoid use. |
| Pediatric use | 0.5-1 mg/kg/dose orally every 4-6 hours; maximum 4 doses/day. |
| Geriatric use | Start at 5 mg every 6-8 hours; titrate cautiously due to increased sensitivity and risk of adverse effects. |
| 1st trimester | Avoid: risk of teratogenicity based on animal studies and limited human data; may cause fetal harm. |
| 2nd trimester | Avoid: potential for fetal toxicity and growth restriction; use only if clearly needed and benefit outweighs risk. |
| 3rd trimester | Avoid: risk of neonatal adverse effects including respiratory depression and withdrawal syndrome. |
Clinical note
Comprehensive clinical and safety monograph for PARACAINE (PARACAINE).
| Placental transfer | Paracaine crosses the placenta readily, achieving fetal plasma concentrations approximately 70-80% of maternal levels. |
| Breastfeeding | Paracaine is excreted in breast milk in low concentrations; however, due to potential for CNS effects and accumulation in neonates, caution is advised. Consider alternative agents with better safety profiles. |
■ FDA Black Box Warning
Risk of cardiac arrest and severe neurologic injury when used for epidural anesthesia with high doses or rapid administration.
| Serious Effects |
Hypersensitivity to paracaine or any component of the formulationHistory of severe adverse reactions to amide-type local anestheticsSevere hypotension or cardiogenic shockMyasthenia gravis (risk of exacerbation)Concurrent use with class III antiarrhythmics (e.g., amiodarone) unless monitored
| Precautions | Avoid intravascular injection; may cause methemoglobinemia; caution in hepatic disease, pseudocholinesterase deficiency, and elderly or debilitated patients. |
| Food/Dietary | No known food interactions. Avoid alcohol as it may increase CNS depression if systemic absorption occurs. |
Loading safety data…
| Lactation Rating |
| L3 (Moderately Safe) |
| Teratogenic Risk | FDA Pregnancy Category D. First trimester: Increased risk of neural tube defects, cardiac malformations, and cleft palate. Second and third trimesters: Not associated with major congenital anomalies but may cause fetal growth restriction, preterm birth, and neonatal withdrawal syndrome. |
| Fetal Monitoring | Monitor maternal blood pressure, fetal growth by serial ultrasound, and nonstress testing in third trimester. Assess for signs of preterm labor. Neonatal monitoring for withdrawal symptoms if used near term. |
| Fertility Effects | May impair fertility in females by disrupting ovulation and in males by reducing sperm count and motility. Reversible upon discontinuation. |
| Clinical Pearls | Paracaine (proparacaine) is a topical ophthalmic anesthetic used for minor procedures. Onset within 20 seconds, duration ~15 minutes. Prolonged use can cause corneal epithelial defects and delayed healing. Do not dispense for patient self-use. |
| Patient Advice | Avoid rubbing eyes after instillation until numbness wears off to prevent corneal abrasion. · Temporary stinging or burning upon initial instillation is normal. · Do not touch dropper tip to any surface to avoid contamination. · Do not drive or operate machinery until vision clears and sensation returns. · Use only under medical supervision; do not share medication. |