ISOCAINE HYDROCHLORIDE
Clinical safety rating: caution
Comprehensive clinical and safety monograph for ISOCAINE HYDROCHLORIDE (ISOCAINE HYDROCHLORIDE).
Isocaine hydrochloride is a local anesthetic that stabilizes neuronal membranes by blocking voltage-gated sodium channels, thereby inhibiting the initiation and propagation of action potentials.
| Metabolism | Primarily via hepatic esterases (plasma pseudocholinesterase) to produce para-aminobenzoic acid (PABA) and diethylaminoethanol. |
| Excretion | Renal: Approximately 90% of the dose is excreted as metabolites (primarily conjugated with glucuronic acid) in urine. Fecal: About 10% eliminated unchanged or as metabolites in feces. Biliary excretion is negligible. |
| Half-life | Terminal elimination half-life is approximately 2.5 hours in healthy adults. In patients with hepatic impairment, half-life may be prolonged to 6–8 hours; in severe renal impairment, half-life may extend to 4–6 hours. |
| Protein binding | Approximately 70–80% bound to plasma proteins, primarily to albumin and alpha-1-acid glycoprotein. |
| Volume of Distribution | Vd is approximately 1.5–2.0 L/kg, indicating extensive tissue distribution. Clinical meaning: High Vd suggests rapid distribution into peripheral tissues, which may influence loading dose requirements. |
| Bioavailability | Subcutaneous: 100% (complete absorption from injection site). Epidural: 100% (directly into systemic circulation). Oral: Not available due to extensive first-pass metabolism. |
| Onset of Action | Intravenous: 30–60 seconds. Epidural: 5–15 minutes. Subcutaneous infiltration: 1–5 minutes. |
| Duration of Action | Intravenous: 15–30 minutes (single dose). Epidural: 60–90 minutes (with epinephrine). Subcutaneous infiltration: 30–60 minutes (with epinephrine). Duration prolonged by addition of epinephrine. |
1-2% solution infiltrated subcutaneously or locally, maximum dose 4.5 mg/kg (with epinephrine) or 3.0 mg/kg (without epinephrine), not to exceed 300 mg.
| Dosage form | INJECTABLE |
| Renal impairment | No specific adjustment required; use with caution in severe renal impairment (eGFR <30 mL/min) due to risk of accumulation of metabolites. |
| Liver impairment | Child-Pugh Class A: No adjustment; Child-Pugh B: Reduce dose by 50% and monitor for toxicity; Child-Pugh C: Avoid use due to decreased metabolism. |
| Pediatric use | Weight-based: 0.5-1% solution infiltrated subcutaneously or locally, maximum 2.0 mg/kg with epinephrine, 1.5 mg/kg without epinephrine; maximum total dose 100 mg. |
| Geriatric use | Reduce dose by 20-30% due to decreased hepatic clearance and increased sensitivity; maximum dose 3.5 mg/kg with epinephrine, 2.5 mg/kg without epinephrine. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for ISOCAINE HYDROCHLORIDE (ISOCAINE HYDROCHLORIDE).
| Breastfeeding | Mepivacaine is excreted into breast milk in trace amounts; M/P ratio is approximately 0.4. It is considered compatible with breastfeeding with minimal risk. Caution with repeated doses in infants. |
| Teratogenic Risk | Isocaine hydrochloride (mepivacaine) is classified as FDA Pregnancy Category C. In first trimester, animal studies have shown fetal harm but no adequate human studies; use only if clearly needed. Second and third trimesters: no known teratogenicity, but may cause fetal bradycardia and decreased uterine blood flow due to vasoconstriction; use lowest effective dose. |
■ FDA Black Box Warning
Not available (no FDA boxed warning identified for this drug).
| Serious Effects |
["Hypersensitivity to Isocaine hydrochloride or any ester-type local anesthetic","Hypersensitivity to para-aminobenzoic acid (PABA) or its derivatives","Severe hypotension or complete heart block","Infection at the injection site"]
| Precautions | ["Risk of systemic toxicity if administered intravascularly or in excessive doses","Caution in patients with hepatic disease, pseudocholinesterase deficiency, or cardiovascular disease","Avoid use in patients with known hypersensitivity to ester-type local anesthetics or PABA","Monitor for signs of CNS and cardiac toxicity during administration"] |
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| Fetal Monitoring | Monitor maternal vital signs, ECG, and oxygen saturation. Fetal heart rate monitoring recommended during labor and delivery to detect bradycardia or distress. |
| Fertility Effects | No known adverse effects on fertility in humans. Animal studies have not shown impaired fertility. |