Question

The dilution table of a vial containing 5,000,000 units of penicillin G potassium reads:

Amount of diluent: Units of Penicillin per mL: 9.2 mL 500,000; 4.2 mL 1,000,000; 1.2 mL 2,500,000. How many of diluent should be used to reconsitute the vial so that the concentraton of the obtained solution is 250,000 units/mL? A. 2.0 mL B. 12.2 mL C. 18.4 mL D. 19.2 mL E. 20.0 mL

Answer 1

D. 19.2 mL

Explanation:

The dilution table of a vial containing 5,000,000 units of penicillin G potassium

Calculate the volume occupied by the Penicillin powder in each case.

9.2 mL 500,000

5,000,000 units × mL/500,000 units = 10 mL (volume of reconstituted solution)

Volume occupied by the powder = 10 mL – 9.8 mL = 0.8 mL

4.2 mL 1,000,000

5,000,000 units × mL/1,000,000 units = 5 mL (volume of reconstituted solution)

Volume occupied by the powder = 5 mL – 4.2 mL = 0.8 mL

1.2 mL 2,500,000

5,000,000 units × mL/2,500,000 units = 2mL (volume of reconstituted solution)

Volume occupied by the powder = 2mL – 1.2 mL = 0.8 mL

To reconstitute the vial so that the concentration of the obtained solution is 250,000 units/mL

5,000,000 units × mL/250,000 units = 20 mL

Dry powder occupies 0.8 mL of volume.

Diluent used 20 mL – 0.8 mL = 19.2 mL

19.2 mL diluent should be added to get 250,000 units/mL