Drug calculations

Boomer MS, RN · Jun 16, 2016

Contact pharmacy?

chare · Jun 16, 2016

This link opens a PDF file that you might find helpful.

Drug Calculations

roser13, ASN, RN · Jun 16, 2016

No one can help you with this issue?? That's scary.

Boomer MS, RN · Jun 16, 2016

No one can help you with this issue?? That's scary.

I have never heard of "displacement value." And I took an advanced pharmacology course in graduate school. If anyone knows, help us out here. I want to learn. Otherwise I would go straight to one of the bright pharmacists in my hospital. Perhaps it's not as difficult as it appears? Only way to find out is to ask.

Anonymous865 · Jun 16, 2016

Being a new qualify is not easier!!! my practice educator is on maternity leave, not one seems to know the question. Very painful
The displacement value for co-amoxiclav is 0.9 per 1.2gram Vial. What volume of water for injection would you add to the vial to give a concentration of 60mg in 1 ml?

Here's what I come up with, but I STRONGLY URGE you to check this with someone.

What you have

1.2g Vial

Convert to mg

1.2g x 1000 mg/g = 1200mg

What you want

60 mg

What % of 1200 mg is 60 mg

60 mg / 1200 mg = 0.05 (or 5% or 1/20th)

So you want 1/20th of the solution to be 1ml

20 x 1 ml = 20 ml

You need your total volume to be 20 ml.

Now the displacement value is 0.9. You don't say what units that 0.9 is. I'm assuming that it is 0.9 ml per 1.2 g vial.

20 ml - 0.9 ml = 19.1 ml

You would need to add 19.1 ml to your vial to create 20 ml of solution. Removing 1 ml of that solution should be 60 mg.

Again you should not give this to a patient based on information you got from a stranger on the internet.

Boomer MS, RN · Jun 16, 2016

G

Here's what I come up with, but I STRONGLY URGE you to check this with someone.
What you have
1.2g Vial
Convert to mg
1.2g x 1000 mg/g = 1200mg
What you want
60 mg
What % of 1200 mg is 60 mg
60 mg / 1200 mg = 0.05 (or 5% or 1/20th)
So you want 1/20th of the solution to be 1ml
20 x 1 ml = 20 ml
You need your total volume to be 20 ml.
Now the displacement value is 0.9. You don't say what units that 0.9 is. I'm assuming that it is 0.9 ml per 1.2 g vial.
20 ml - 0.9 ml = 19.1 ml
You would need to add 19.1 ml to your vial to create 20 ml of solution. Removing 1 ml of that solution should be 60 mg.
Again you should not give this to a patient based on information you got from a stranger on the internet.

Good job from a math perspective. Thank you! But nowhere have I ever worked would an RN do this. Pharmacy did ALL the calculations/mixing, even 1:1 insulin drips (How easy is that?), all in the name of safety.

Anonymous865 · Jun 16, 2016

G
Good job from a math perspective. Thank you! But nowhere have I ever worked would an RN do this. Pharmacy did ALL the calculations/mixing, even 1:1 insulin drips (How easy is that?), all in the name of safety.

Thank you.

I agree with you on Pharmacy doing it. That's why I tried to emphasize that they should not take my solution as gospel.

I figured out how to do it based on the link Chare posted above and by looking at the Prescriber info for that drug.

I suspect OP is doing this for some type of work training as I would hope s/he wouldn't post on the internet to figure out how to reconstitute a med for a live patient. I also suspect OP is in the UK, so nurses might do these calculations there.

Boomer MS, RN · Jun 16, 2016

Thank you.
I agree with you on Pharmacy doing it. That's why I tried to emphasize that they should not take my solution as gospel.
I figured out how to do it based on the link Chare posted above and by looking at the Prescriber info for that drug.
I suspect OP is doing this for some type of work training as I would hope s/he wouldn't post on the internet to figure out how to reconstitute a med for a live patient. I also suspect OP is in the UK, so nurses might do these calculations there.

What you say makes sense. Still fun to see your calculations.

Anonymous865 · Jun 16, 2016

What you say makes sense. Still fun to see your calculations.

I love a good math problem. :sarcastic: