The healthcare provider prescribes penicillin 200,000 units IM for a client with pneumonia. The available vial is labeled, "Penicillin 500,000 units/mL. How many mL should the nurse administer to this client? (Enter numerical value only. If rounding is required, round to the nearest tenth.)

To determine the correct dosage, the nurse needs to perform a calculation using the information provided. The prescription is for 200,000 units of penicillin, and the available vial concentration is 500,000 units per mL. To find out how many mLs to administer, the nurse would divide the prescribed units by the concentration of units per mL. This is calculated as 200,000 units divided by 500,000 units/mL, which equals 0.4 mL.