# Easiest drug calculation method?

- 0Sep 21, '07 by
*MiaKeaRN*I'm preparing for my first drug calculation test and am hoping for some input on what others think is the easiest drug calc method/formula. I have always, always, always struggled in math.....so the easier the better for me. We are not taught a particular method, just given the names of some books and basically we are teaching ourselves.

Thanks.

p.s. I know there are older posts for drug calc suggestions, but I am basically interested in the students who are now dealing with this now.Last edit by MiaKeaRN on Sep 21, '07 - 1Sep 21, '07 by sweetjean143Quote from MiaKeaI'm preparing for my first drug calculation test and am hoping for some input on what others think is the easiest drug calc method/formula. I have always, always, always struggled in math.....so the easier the better for me. We are not taught a particular method, just given the names of some books and basically we are teaching ourselves.

Thanks.

p.s. I know there are older posts for drug calc suggestions, but I am basically interested in the students who are now dealing with this now.

The formula method is the easiest for me. I find it simpler to plug numbers in than to try to decide what goes on what side of the equation. I am in med math right now, and my teacher is very clear and concise and makes it very easy to learn. If you need any help let me know.MiaKeaRN likes this. - 1Sep 21, '07 by MegNeoNurseFor basic med admin: dose ordered/dose on hand X vehicle (e.g. 5mL).

So for example, order states Ativan 0.5mg IV. Pharmacy sends vial which contains Ativan 3mg per 1 mL.

Your formula would be 0.5mg/3mg X 1mL = 0.2 mL

Drip rate calculations.....

mL to be admin/# of hours X gtt/mL x 1hr/60min (if it is a drip/min calc, otherwise omit last part of formula)MiaKeaRN likes this. - 1Sep 21, '07 by mystykstarFor me the easiest method, even though you are repeating yourself a little because d/h X V actually erases a few steps. but I use have/vehicle=desired/the actual amount that you need (X) and then you cross multiply which would be d x v = h x (x) and then you would use basic alegebra to finish the problem. I personally need the extra steps to make sure that I am right instead of taking the shortcut. I hoped I helped a little and didn't confuse you!!MiaKeaRN likes this.
- 1Sep 21, '07 by kstecI put this on another post on calculating doses. I worked in a pharmacy for 14 years and these two formulas were mostly used by the pharmacists.

Take what you want, divided by what you have and multiply by the quantity/volume.

Example1: Doctor orders 125mg of amoxicillin, your stock is 250mg/5ml

want 125mg divided by 250mg multiplied by 5=2.5ml

Example2: Simple cross multiplication

Stock__250mg__=__125mg__

5ml X

__250mgX=625__625+250=2.5ml

250 250

Hope this helps and if you need help let me know, or if this is something you already know this, I apologize.MiaKeaRN likes this. - 0Sep 22, '07 by
*Daytonite*Mia. . .the basicthat works for just about every kind of dosage calculation problem is__formula__

*dose desired divided by the dose you have on hand gives you the dose you are to give to the patient.*

or, shortened is

**dose desired/dose on hand = dose to give**All you have to do is plug the information you are given in the problem into the formula and start doing the math. There are very few instances where you do not need to use this formula. - 1Sep 22, '07 by Jules ADefinitely it is the one that works best for you. I prefer means and extremes (example below) because it lays it down in black and white for me to check both sides of the equation. Often I will double check it with D/H X Q but other the other method I've seen totally confuses me.

3ml : 200mg = X : 300mgMiaKeaRN likes this. - 1Sep 22, '07 by CT Pixie, ASN, RNEX: ordered is 15mg po tix. supply is 30mg tabs.

The way I figure it out (don't recall what the actual name is) is like this

I set up my supply side (known..30mg tabs). Then ='s my order 25mg and put that over X since how many to give is the unknown right now

__30mg = 15mg__

1 tab x

cross multiply and get 30X=15. Isolate X by divinding both sides by 30 and I get X= how much to give.. 1/2 tabMiaKeaRN likes this.