Drug Calculations: what works for you??

BacktotheBeach, ADN, BSN, RN · Feb 5, 2011

I am terrible at math, I dread it and am terrified of it!! But, I am successful at dosage so far in NS by using ratio and proportion exclusively. All you need to know is that method and you are golden!! I really think if a math-a-phobe like me can master this, anyone can.

And what works the best is practice, practice, practice. I mean tons and tons of problems. My school gives out worksheets like mad, and the people that don't do a lot of problems are not successful, usually. We had a girl with a previous bachelor's degree, who had college calculus and she failed a dosage test and was out of the program!! This is a whole different animal.

KimberlyRN89, BSN, RN · Feb 5, 2011

I am terrible at math, I dread it and am terrified of it!! But, I am successful at dosage so far in NS by using ratio and proportion exclusively. All you need to know is that method and you are golden!! I really think if a math-a-phobe like me can master this, anyone can.
And what works the best is practice, practice, practice. I mean tons and tons of problems. My school gives out worksheets like mad, and the people that don't do a lot of problems are not successful, usually. We had a girl with a previous bachelor's degree, who had college calculus and she failed a dosage test and was out of the program!! This is a whole different animal.

I totally agree with you! I suck @ math too, but I am actually doing quite well in Dosage & Calculation this semester & I think its because of practice, practice, practice like you've mentioned. At first I was terrified of this class, but I think if you put a lot of effort into it, you will do fine:heartbeat:up: :nurse:

mspontiac · Feb 6, 2011

I am terrible at math, I dread it and am terrified of it!! But, I am successful at dosage so far in NS by using ratio and proportion exclusively. All you need to know is that method and you are golden!! I really think if a math-a-phobe like me can master this, anyone can.
And what works the best is practice, practice, practice. I mean tons and tons of problems. My school gives out worksheets like mad, and the people that don't do a lot of problems are not successful, usually. We had a girl with a previous bachelor's degree, who had college calculus and she failed a dosage test and was out of the program!! This is a whole different animal.

I am also "math challenged," and I use the exact same method you use. I *always* use a ratio/proportion formula and I excelled on my dosage exam and never have a problem with calculations. My former Med-Surg I instructor taught us to do it this way.

I read the problem and ask myself, what do I need? What do I have? That allows me to toss out unneeded info that is placed in there to throw me off. So say I have a problem like this:

"Potassium chloride is available as 16 g per tablet. Potassium Chloride (K-Dur), 8 g, is ordered. How many tablets would the nurse administer?"

I ask myself what I have: 16 gram tablets. I ask myself what I need: 8 grams. So I set up the proportion like this (sorry, it's difficult to type a proportion on a computer screen and have it look right):

1 tab = ? tab

_____ ______

16 g = 8 g

Then cross multiply and divide to get the answer - 8 x 1 divided by 16 = 0.5 tablets.

It is also vital that the student knows conversions.

live&love&heal · Feb 6, 2011

As an LVN who is now in RN school, I just recently found what works for me.

Here are my answers to your questions:

1. What your struggles were (what exactly you had trouble with)

- Memorizing formulas and conversions.

- In LVN school they taught us the 3 ways to solve drug calcs (formulas, ratio/proportion, and dimensional analysis). It was really confusing to try to determine which method was best. I just a combination of formulas and ratio/proportion.

- Trying to find what values were needed to solve the problem. I get confused what values to use when distractors are in the problem because, I can't distinguish what information is relevant to use to solve the problem and what isn't relevant.

2. What worked for you (how you overcame your difficulties, assuming you did):

- I'm using Dimensional Analysis. It's simple and straightforward. It also eliminates the need to memorize formulas. Also, I only stuck to 1 way to solve problems. much simpler and less confusing.

- For memorization of conversions, I simply just do as many problems that have conversions and keep practicing. I also wrote down the common conversions that I need to memorize and made a flashcard to memorize them.

- Practice, practice, practice. I have been doing as many problems as a I can and this has helped me to drill myself and become familiar with what exactly is being asked to solve. So far it's worked!

Aberdeen · Feb 6, 2011

I was taught dimensional analysis, which to me is much easier. Using the example above I would set the problem up this way:

tabs/dose= 1 tab/16g X 8g = 8/16 = 0.5 tabs

Once the problem is set up then you just multiply straight across, and then divide. Also “tabs/dose” is the same as saying “# of tabs per dose”, and you can also use “8g/1” since it would be equal to “8g” if you want to have everything in fraction form.

Another example with a conversion:

Order: Atropine 0.3 mg IM now

Label: Atropine 400 mcg/mL

How many mL would be administered?

mL/dose = 1 mL/400 mcg X 1,000 mcg/ 1mg X 0.3 mg = 300/400 = 0.75 mL

It is a bit hard to see typed out, but when you re-write them and see the numerator actually on top of the denominator it becomes easier to see what is being multiplied by what. I also agree with the others that it takes practice and knowing your conversions is a must! Not knowing conversions is the one thing I have seen that causes most people to fail. They set the problems up correctly, but use the wrong conversion factors, thus they end up with the wrong answer. I don’t know if this helps or not and I sure hope it doesn’t confuse anyone who reads it, but it is what I have used to pass every med calc test.

Jonathank · Feb 6, 2011

I'll cosign practice. And when dimensional analysis gets brought up, that speaks to my larger point: a foundation in all the properties of numbers is REALLY helpful. Understanding why formulas or operations work is essential, IMHO. For example, in the case of DA- multiplying by the conversion factors (set up as fractions) is the equivalent of multiplying by one, and dividing both the numerators and denominators by the same unit is like dividing by one.

heavenbound · Feb 7, 2011

As for me I prefer dimensional analysis over ratio and proportion. I found it to be easier and the original way I was taught to do math. To offer advice, I'd say decide which method of the three works for you and stick with it. Practice several questions with the the method of your choice until you master it, and then practice some more. Knowing your conversions will make it a lot easier and one less thing you would have to worry about. Learn the conversions by memorizing them and then write them down on your test paper prior to taking the test just in case you forget, because it happens. I hope this helps as it has for me.

ag11 · Feb 7, 2011

oddly enough..I am really good in Math (wish i was the same with lecture exams loool) but I do notice w/ others at my school is that if they can see first hand "WHY" the formula is set up a certain way..broken up first..explained..then solve..I find that this method worked the most when helping out with med math.