Question

ordered: rocephin 500 mg IM bid. available: rocephin 0.5 g vial. directions: add 1.8 mL of diluent to yield 250 mg/mL. Add 1 mL of diluent to yield 350 mg/mL. How many mL will you give if you add 1 mL of diluent?

Answer 1

To give 500 mg of rocephin with a concentration of 350 mg/mL after adding 1 mL of diluent, approximately 1.43 mL of the solution should be administered.

Step-by-step explanation:

The student has been prescribed rocephin 500 mg IM bid, which is available as a 0.5 g vial. According to the directions provided, adding 1.8 mL of diluent yields 250 mg/mL, while adding 1 mL of diluent yields 350 mg/mL. The student asks how many mL to administer if 1 mL of diluent is added to the vial.

To calculate this, we use the given concentration with 1 mL of diluent, which yields 350 mg/mL. Since 0.5 g equals 500 mg, the doctor has ordered 500 mg per dose. Therefore, to administer a 500 mg dose at a concentration of 350 mg/mL, we would calculate the volume needed as follows:

Dose (mg) / Concentration (mg/mL) = Volume (mL)

500 mg / 350 mg/mL = approximately 1.43 mL

Therefore, you would draw up approximately 1.43 mL from the vial to deliver a 500 mg dose of rocephin.