Pharmacy Calculation

Question

Cefuroxime 750mg vials are in stock which when reconstituted with 8mL of diluent yields a concentration of 90mg/mL. A patient undergoing open heart surgery requires 1.5 grams of cefuroxime q12h for 2 days. The dose is to be infused into the vein over a period of 12 hours. The doctor's order states that each dose should be delivered in 250mL of normal saline. What volume of cefuroxime must be injected into each of the bags?

Answer 1

Ans: 16.667 mL

This is an example of "amount to be administered"... While there is a great deal of information presented, the REAL question is simply: "What volume of cefuroxime must be injected into each of the (IV) bags?"

The basic med math formula determines the amount of fluid (mL) that is needed when the cefuroxime is reconstituted. This information is derived from clues the first sentence: "Cefuroxime 750mg vials are in stock which when reconstituted with 8mL of diluent yields a concentration of 90mg/mL" We are being asked how much cefuroxime to inject in the bag of IV fluid and we know we want to have 1.5gm (1500mg) for the 12-hour infusion. So we know the volume on hand in the resultant constitution mix is 1 mL and the concentration on hand is 90mg. These values are entered into the basic equation:

Vol (mL) / conc (mg) x desired dose (mg) = amt (mL) to administer.

1mL/90mg x 1500mg = 16.6666666 mL