MEPIVACAINE HYDROCHLORIDE
Clinical safety rating: caution
Comprehensive clinical and safety monograph for MEPIVACAINE HYDROCHLORIDE (MEPIVACAINE HYDROCHLORIDE).
Mepivacaine hydrochloride is an amide-type local anesthetic that reversibly blocks nerve impulse propagation by binding to sodium channels in the neuronal cell membrane, thereby stabilizing the membrane and preventing depolarization.
| Metabolism | Metabolized primarily in the liver via cytochrome P450 enzymes, particularly CYP1A2 and to a lesser extent CYP3A4. Major metabolites include p-hydroxymepivacaine and N-demethylated derivatives. |
| Excretion | Primarily hepatic metabolism via amidase enzymes; ~95% excreted as metabolites in bile and feces, <5% unchanged in urine. |
| Half-life | Terminal elimination half-life approximately 2 hours (range 1.5–3 hours). In neonates and patients with hepatic dysfunction, half-life may be prolonged up to 8–10 hours. |
| Protein binding | Approximately 75–78% bound, primarily to alpha-1-acid glycoprotein. |
| Volume of Distribution | 0.8–1.0 L/kg. Reflects moderate distribution; higher values may indicate reduced protein binding or increased tissue uptake. |
| Bioavailability | Systemic bioavailability after epidural or peripheral nerve block is approximately 100% due to vascular absorption; oral bioavailability is very low (<10%) due to extensive first-pass metabolism. |
| Onset of Action | Infiltration: within 1–2 minutes; Epidural: 5–15 minutes; Peripheral nerve block: 10–20 minutes. |
| Duration of Action | Infiltration: 0.75–1.5 hours; Epidural: 1–2 hours; Peripheral nerve block: 1–3 hours. Duration is extended with epinephrine (up to 50% longer). |
1-2% solution, 5-20 mL local infiltration or nerve block, maximum 400 mg per procedure.
| Dosage form | INJECTABLE |
| Renal impairment | No dose adjustment required, as mepivacaine is hepatically metabolized. |
| Liver impairment | Child-Pugh A: no adjustment. Child-Pugh B: reduce dose by 50%. Child-Pugh C: contraindicated. |
| Pediatric use | 0.5-2 mg/kg per dose, maximum 5 mg/kg cumulative. |
| Geriatric use | Reduce dose by 20-40%, use lower concentrations and volumes, monitor for toxicity. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for MEPIVACAINE HYDROCHLORIDE (MEPIVACAINE HYDROCHLORIDE).
| Breastfeeding | Mepivacaine is excreted into breast milk in small amounts; the milk-to-plasma (M/P) ratio is approximately 0.5-1.0. The relative infant dose is <1% of the maternal dose, and adverse effects in nursing infants are unlikely with occasional use. However, caution is advised due to possible accumulation in infants with impaired hepatic function. |
| Teratogenic Risk | Mepivacaine hydrochloride is classified as FDA Pregnancy Category C. In the first trimester, no well-controlled human studies exist, but animal studies have shown fetal harm at high doses. In the second and third trimesters, use is generally avoided due to potential fetal acidosis and bradycardia from rapid placental transfer. Risk of fetal bradycardia is highest with paracervical block. |
■ FDA Black Box Warning
Not available.
| Serious Effects |
["Hypersensitivity to mepivacaine or other amide-type local anesthetics","Severe hypotension","Complete heart block or severe conduction abnormalities","Severe hepatic disease","Myasthenia gravis (relative contraindication)","Children under 6 months of age (relative contraindication, due to increased risk of methemoglobinemia)"]
| Precautions | ["Risk of cardiac arrest and respiratory arrest if administered intravenously or in excessive doses","Use with caution in patients with hepatic impairment","Use with caution in patients with severe renal impairment","May cause methemoglobinemia, especially in infants and patients with glucose-6-phosphate dehydrogenase deficiency","Avoid use in patients with hypersensitivity to amide-type local anesthetics","Monitor for signs of central nervous system toxicity (e.g., seizures, loss of consciousness) and cardiovascular toxicity (e.g., hypotension, bradycardia)"] |
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| Fetal Monitoring | Monitor maternal heart rate, blood pressure, and respiratory status continuously during administration. Fetal heart rate monitoring is recommended during paracervical or epidural block to detect bradycardia. Observe for signs of systemic toxicity in the mother, including CNS excitation or depression and cardiotoxicity. |
| Fertility Effects | No specific human studies on fertility effects. Animal studies have not shown impaired fertility. However, repeated high-dose local anesthetics may theoretically affect sperm motility or ovarian function, but clinically insignificant at therapeutic doses. |