What is the toxic dose of lidocaine without epinephrine?

What is the toxic dose of lidocaine without epinephrine?

• A. 200 mg.
• B. 300 mg.
• C. 500 mg.
• D. 1000 mg.

Answer: (B)

The key point is the maximum safe dose of lidocaine when no vasoconstrictor is used. Without epinephrine, lidocaine is absorbed more quickly, so the threshold at which toxicity can occur is lower. For an average adult, the commonly cited maximum safe dose is about 4.5 mg per kilogram, which translates to roughly 300 mg for a typical 70 kg patient. This is why 300 mg is the best answer: it represents the practical ceiling before systemic toxicity becomes a real concern. A smaller amount like 200 mg stays well under that limit, while larger amounts such as 500 mg or 1000 mg exceed the recommended ceiling for lidocaine without epinephrine and carry a higher risk of toxic effects, including CNS symptoms and cardiovascular issues. (If epinephrine were used, higher total doses could be considered safe, but the question specifies without epinephrine.)

The key point is the maximum safe dose of lidocaine when no vasoconstrictor is used. Without epinephrine, lidocaine is absorbed more quickly, so the threshold at which toxicity can occur is lower. For an average adult, the commonly cited maximum safe dose is about 4.5 mg per kilogram, which translates to roughly 300 mg for a typical 70 kg patient. This is why 300 mg is the best answer: it represents the practical ceiling before systemic toxicity becomes a real concern.

A smaller amount like 200 mg stays well under that limit, while larger amounts such as 500 mg or 1000 mg exceed the recommended ceiling for lidocaine without epinephrine and carry a higher risk of toxic effects, including CNS symptoms and cardiovascular issues. (If epinephrine were used, higher total doses could be considered safe, but the question specifies without epinephrine.)