Question

ceftriaxone (rocephin) is a dry powder antibiotic that must be reconstituted for use. the label states that to create a 100 mg/ml solution, 4.8 ml must be added to a 500mg vial. what is the powder volume.

I am not sure what formula to use for this problem. How do I go about solving this?

Answer 1

???
if 4.8 ml must be added, I'd say the volume is 4.8 ml

What am I missing? or, How has the question been garbled? Maybe you should clarify just what the named volumes comprise.

Answer 2

im not sure, all I know is the answer is .2 but I have no clue as to how they got it.

Answer 3

someone answered the question. this is what they said:

When you add a volume to a powder, the powder does displace the liquid some. In this case, 0.2 ml.

If the powder had no volume, normally you would add 5 ml to 500 mg to get 100 mg/ml. But the combination of the powder and the diluent gives you 100 mg/ml.

5 ml (what would give you the theoretical correct dilution if there was not a large volume in the vial) - 4.8 ml (actual volume added) = 0.2 ml.

However I do not know where they got the 5 ml from.