Year 12s: what will be the first way you research your future options? >>

Help- Drug Dilution calculations

eliza.louise.mc

Hello, in my first year approaching exams this Jan and can not get my head round drug dilution calculations. I get as far as calculating the mass using m=cv and then I have no idea how to proceed (there are instructions provided but I still don't get it). Any help would be muchos appreciated. ImageUploadedByStudent Room1451470117.235140.jpg

ImageUploadedByStudent Room1451470117.235140.jpg

Posted from TSR Mobile

Reply 1

Helenia

Well, I've no idea what the "official" way of doing it is, but here's how I'd approach it.

To work out what mass you need, work out 0.15% in mg/ml. A percentage w/v (weight/volume) just tells you how many grams of drug there is per 100ml of solution, expressed as a percentage rather than mg/ml. So 1% means 1g/100ml.
0.15% = 0.15g (or 150mg) in 100ml
Therefore 150/100 = 1.5mg/1ml of solution.
You need 10mls, so need to end up with a total of 15mg of drug in 10mls solution.

Three of the four stock solutions you have listed there are too dilute to achieve this, so you must use the 2nd bottle on the list - the one containing 10mg/ml solution (the size of this container does not matter). To get 15mg of drug, you need 15/10 = 1.5 mls of that solution.

You then have the right amount of drug, and just need to dilute it up to make 10mls of the new solution. So add 8.5mls of water for injections (assuming that is the correct diluent!) and bingo!