What is the toxic dose of lidocaine when used with epinephrine?

What is the toxic dose of lidocaine when used with epinephrine?

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

Answer: (C)

Epinephrine slows lidocaine entering the bloodstream by causing local vasoconstriction, which lowers peak plasma levels and lets you use a higher total dose safely. For lidocaine with epinephrine, the commonly cited maximum safe dose is about 7 mg per kilogram, with a practical cap of roughly 500 mg in a healthy adult. This is why 500 mg is the best choice for the toxic-dose context. Without epinephrine, the limit is lower—about 4.5 mg/kg (around 300 mg for many adults)—because there’s no vasoconstriction to slow absorption. Always tailor to individual factors like weight and liver function, but 500 mg with epinephrine is the familiar threshold used in practice and exams.

Epinephrine slows lidocaine entering the bloodstream by causing local vasoconstriction, which lowers peak plasma levels and lets you use a higher total dose safely. For lidocaine with epinephrine, the commonly cited maximum safe dose is about 7 mg per kilogram, with a practical cap of roughly 500 mg in a healthy adult. This is why 500 mg is the best choice for the toxic-dose context. Without epinephrine, the limit is lower—about 4.5 mg/kg (around 300 mg for many adults)—because there’s no vasoconstriction to slow absorption. Always tailor to individual factors like weight and liver function, but 500 mg with epinephrine is the familiar threshold used in practice and exams.