POLOCAINE-MPF
Clinical safety rating: caution
Comprehensive clinical and safety monograph for POLOCAINE-MPF (POLOCAINE-MPF).
Polocaine-MPF (mepivacaine hydrochloride) is an amide-type local anesthetic that blocks sodium ion channels in nerve cell membranes, thereby preventing the initiation and propagation of nerve impulses. This results in reversible loss of sensation in the area of administration.
| Metabolism | Primarily hepatic via N-demethylation by CYP1A2 and CYP3A4; minor metabolism by amidases. |
| Excretion | Renal: >90% as metabolites, primarily 4-hydroxy-2',6'-dimethylacetanilide and pipecoloxylidide; unchanged drug <5%. Biliary/fecal: <5%. |
| Half-life | Terminal elimination half-life: 1.5-2.0 hours in adults; prolonged in hepatic impairment (up to 4-6 hours) and severe renal impairment. Clinical context: short half-life supports continuous infusion for sustained effect. |
| Protein binding | 70-80% bound primarily to alpha-1-acid glycoprotein (AAG) and albumin. Binding increases with AAG levels (e.g., stress, surgery, malignancy). |
| Volume of Distribution | Vd: 0.8-1.5 L/kg. Clinical meaning: extensive tissue distribution (highly perfused organs); rapid redistribution accounts for short IV half-life. |
| Bioavailability | Bioavailability: IV: 100%; epidural: near 100% (dose-dependent systemic absorption); peripheral nerve block: near 100%; oral: <30% due to extensive first-pass hepatic metabolism (not used orally). |
| Onset of Action | Intravenous: 45-90 seconds; epidural: 5-15 minutes; peripheral nerve block: 5-10 minutes; infiltration: 0.5-2 minutes. |
| Duration of Action | Intravenous: 10-20 minutes (rapid redistribution); epidural: 60-120 minutes (with epinephrine: 90-150 minutes); peripheral nerve block: 60-180 minutes (with epinephrine: up to 300 minutes). Duration increases with dose and addition of vasoconstrictors. |
Adults: 1-2 cartridges (1.8 mL each) of 2% lidocaine with 1:100,000 epinephrine administered via local infiltration or nerve block, not to exceed 7 mg/kg (maximum 500 mg) for lidocaine.
| Dosage form | INJECTABLE |
| Renal impairment | No specific dose adjustment required for mild to moderate renal impairment. For severe renal impairment (GFR <30 mL/min), consider reducing dose due to potential accumulation of metabolites; maximum single dose of lidocaine should not exceed 4.5 mg/kg. |
| Liver impairment | For Child-Pugh Class B: reduce dose by 50%. For Child-Pugh Class C: reduce dose by 75% or avoid use due to significant reduction in lidocaine metabolism. |
| Pediatric use | Maximum lidocaine dose: 4.5 mg/kg total body weight (including epinephrine). For local infiltration, typical 1% solution at 0.5-2 mg/kg per injection, not to exceed 4.5 mg/kg per session. |
| Geriatric use | Elderly patients may require reduced doses due to decreased hepatic metabolism and increased sensitivity. Maximum dose should not exceed 4.5 mg/kg, with careful titration and monitoring for CNS and cardiovascular side effects. Dose interval may be extended. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for POLOCAINE-MPF (POLOCAINE-MPF).
| Breastfeeding | Mepivacaine is excreted into breast milk in small amounts. M/P ratio is approximately 0.4-0.6. The relative infant dose is less than 4% of maternal weight-adjusted dose. Considered compatible with breastfeeding, but observe infant for signs of local anesthetic toxicity (e.g., drowsiness, irritability). |
| Teratogenic Risk | POLOCAINE-MPF (mepivacaine) is classified as FDA Pregnancy Category C. In first trimester, risk cannot be ruled out; teratogenic effects observed in animal studies at high doses. In second and third trimesters, use only if clearly needed; may cause fetal bradycardia and central nervous system depression. Avoid paracervical block in pregnancy due to high risk of fetal acidosis and bradycardia. |
■ FDA Black Box Warning
There is no FDA black box warning for Polocaine-MPF.
| Serious Effects |
["Hypersensitivity to mepivacaine or other amide anesthetics","Severe hypotension or complete heart block","Myasthenia gravis relative contraindication"]
| Precautions | ["Risk of seizures and cardiac arrest if accidentally injected intravascularly","Caution in patients with hepatic impairment due to reduced metabolism","Caution in patients with cardiovascular disease due to potential myocardial depression and hypotension","Avoid use in patients with known hypersensitivity to amide-type local anesthetics","Not recommended for obstetric paracervical block due to fetal bradycardia risk"] |
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| Fetal Monitoring | Monitor maternal blood pressure, heart rate, and oxygen saturation. Fetal heart rate monitoring is recommended during administration, especially in third trimester. Assess for signs of systemic toxicity (e.g., seizures, arrhythmias) in mother and fetus. In case of paracervical block, continuous fetal monitoring is mandatory. |
| Fertility Effects | Animal studies have shown no significant impairment of fertility at clinically relevant doses. No human data on fertility effects. Theoretical risk of transient hormonal changes with systemic absorption, but not clinically relevant for local administration. |