Among the listed local anesthetics, which has a maximum dose of 90 mg for a 70 kg adult?

• A. Lidocaine 300 mg
• B. Mepivacaine 300 mg
• C. Bupivacaine 90 mg
• D. Prilocaine 600 mg

Answer: (C)

The concept here is that each local anesthetic has a maximum recommended dose to prevent systemic toxicity, and the limit varies by drug because of differences in potency and cardiotoxic risk. Bupivacaine is more potent and longer lasting but carries a higher risk of cardiac toxicity, so its safe total dose is kept relatively low. For a 70 kg adult, 90 mg translates to about 1.3 mg/kg, which is much lower on a per-kilogram basis than what’s used for the other agents. That’s why bupivacaine has the 90 mg maximum in this context. The other drugs have higher maximums (around 300 mg for lidocaine and mepivacaine, and about 600 mg for prilocaine), so they don’t fit the stated maximum dose for a 70 kg patient.