In a 1:100,000 epinephrine local anesthetic, how many milligrams of lidocaine and epinephrine are present?

• A. 40 Mg of Xylocaine and 0.020 Mg of epi
• B. 36 Mg of Xylocaine and 0.018 Mg of epi
• C. 32 Mg of Xylocaine and 0.015 Mg of epi
• D. 50 Mg of Xylocaine and 0.025 Mg of epi

Answer: (B)

Understanding how a percentage and dilution translate into milligrams per cartridge is the key. A standard dental cartridge is 1.8 mL.

Lidocaine amount starts from its concentration: 2% lidocaine equals 2 g per 100 mL, which is 20 mg per mL. Multiply by 1.8 mL: 20 mg/mL × 1.8 mL = 36 mg of lidocaine.

Epinephrine at 1:100,000 means 0.01 mg per mL. Multiply by 1.8 mL: 0.01 mg/mL × 1.8 mL = 0.018 mg of epinephrine.

So, per cartridge, you have 36 mg of lidocaine and 0.018 mg of epinephrine.