For post-cardiac arrest, mixing 1 mg of 1:1000 epinephrine with 500 mL normal saline yields what concentration?

• A. 1 mcg/mL
• B. 2 mcg/mL
• C. 0.5 mcg/mL
• D. 5 mcg/mL

Answer: (B)

Dilution and unit conversion are at play here. Epinephrine 1:1000 is 1 mg per mL. Taking 1 mg of that solution means using 1 mL of the stock. Dilute into 500 mL of normal saline gives a final volume of about 501 mL, so 1000 mcg are distributed over roughly 501 mL. 1000 / 501 ≈ 1.996 mcg/mL, essentially 2 mcg/mL. Even if you approximate the total volume as 500 mL, you’d have 1000 mcg in 500 mL, which is 2 mcg/mL.