1. A nurse is preparing to administer codeine 20 mg PO every 6 hr PRN pain. Available is codeine oral solution 10 mg/ 5 mL. How many mL should the nurse administer per dose? (Round to the nearest whole number. Use a leading zero if it applies. Do not use atrailing zero.) Answer: 10 mL Follow these steps for the Ratio and Proportion method of calculation: Step 1: What is the unit of measurement the nurse should calculate? mL Step 2: What is the dose the nurse should administer? Dose to administer = Desired 20 mg Step 3: What is the dose available? Dose available = Have 10 mg Step 4: Should the nurse convert the units of measurement? No Step 5: What is the quantity of the dose available? 5 mL Step 6: Set up an equation and solve for X. Have/Quantity = Desired/X 10 mg/ 5 mL = 20 mg/ X mL X mL = 10 mL Step 7: Round if necessary.