A 150-pound patient has received two cartridges of 2% lidocaine, 1:100,000 epinephrine. How many additional cartridges with the same drugs can be administered before reaching the MRD?
A) 5
B) 6
C) 9
D) 11

Question

Quizplus · Accepted Answer

The maximum recommended dose (MRD) of lidocaine with epinephrine for a healthy adult is 7 mg/kg. For a 150-pound patient (approximately 68 kg), this equates to 476 mg (68 kg x 7 mg/kg). Each cartridge of 2% lidocaine with 1:100,000 epinephrine contains 36 mg of lidocaine (1.8 mL x 20 mg/mL). Having already received two cartridges (72 mg), the patient can receive up to 404 mg more lidocaine. Dividing this by 36 mg per cartridge gives approximately 11.2 cartridges. Since the patient can only receive whole cartridges, they can receive 11 more cartridges, but since the question asks for additional cartridges beyond the initial two, the correct answer is 9 additional cartridges.

A 150-Pound Patient Has Received Two Cartridges of 2% Lidocaine