LAs’ nonselective voltage-gated sodium channel blockade is responsible not only for its therapeutic effect but also for most of its adverse effects. High plasma levels, other than overdose, may be caused by (1) repeated doses, (2) rapid absorption, (3) intravascular injection, (4) low plasma protein binding, and (5) slow clearance.2,6-10,19-21 The dosage for healthy adults is based on body weight; however, if a patient’s weight is ≥150 lbs. no more than the maximum recommended dose (MRD) should be administered (Table 5).4-10,19-21
Dosing must also take into considerations the dose of epinephrine or levonordefrin in a LA formulation. To minimize medication errors, it is prudent to think of dosage strengths in mg/mL rather than ratio expressions, e.g., 1:100,000 (Table 5). The maximum recommended dose (MRD) of epinephrine in healthy adults is 0.2 mg per visit.13 Levonordefrin, 0.05 mg, is bioequivalent to epinephrine, 0.01 mg; consequently, the MRD of levonordefrin is 1 mg.17 In high-risk populations, a dose of 0.02 to 0.05 mg of epinephrine is recommended.13
|LA formulations||MRD of LA in mg||LA in mg/mL||500 mg of LA in mL of LA||MRD of EPI in mg||EPI in mg/mL||0.2 mg of EPI in mL of LA|
|Lidocaine 2%||w/ epinephrine 1:100,000||500||20||25||0.2||0.01||20*|
|w/ epinephrine 1:50,000||500||20||25||0.2||0.02||10*|
|Mepivacaine 2%||w/levonordefrin 1:20,000||400||20||20*||1.0||0.02||20*|
|Prilocaine 4%||w/epinephrine 1:200,000||600||40||15*||0.2||0.005||40|
|Articaine 4%||w/epinephrine 1:100,000||500||40||12.5*||0.2||0.01||20|
|Bupivacaine 0.5%||w/epinephrine 1:200,000||90||5||18*||0.2||0.005||40|
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