Adoctor orders 4.5 ml of phenobarbital elixir. if the phenobarbital elixir is available as 20. mg per 7.5 ml, how many milligrams is given to the patient?

In order to find how many milligrams is given to the patient we need to determine the rate by dividing what is available then multiply by the amount that was ordered.

Step 1: (20.0mg / 7.5mL) = 2.66667 mg/mL
Step 2: (2.66667mg/mL x 4.5mL) = 12mg
*Note that mL unit cancels out so we are left with mg

12.0 mg of phenobarbital elixir

The answer is d.potassium