Help with a calculations problem

[kov82]

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How many milliliters of sterile water for injection should be added to a vial containing 5 µg/mL of a drug to prepare a solution containing 1.5 µg/mL of the drug?

could you please show how you would come up with the answer? thanks!

 

[triguitarpharm]

Depends on volume of first vial. C1(V1)=C2(V2+V1),just plug in the volume of the first and solve for V2.

 

[Ackj]

Depends on volume of first vial. C1(V1)=C2(V2+V1),just plug in the volume of the first and solve for V2.

Exactly. You don't have enough info to solve it with what we're given . If it's a 1 ml vial, you'd be adding a different amount of volume than if it was a 10 ml vial. Different amounts of solute.

 

[kov82]

The book answer was 2.33, a pharm tech helped solve it

[5/(x+1) ] = 1.5

x= 2.33

thanks though

 

[Dred Pirate]

ya - there was more information that you didn't give us - obviously it was a 1 ml vial, but you didn't tell us that

 

[kov82]

I wrote the question out as it was written, it was either poorly written or should have been assumed.