# How were you taught to solve this medication calculation problem?

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Hi. I have a question for all of you nursing students who have learned some clinical calculations. I am wondering what method you were taught for solving the problems? I am starting nursing school in August and have been reading Clinical Calculations A Unified Approach by Daniels and Smith. This book teaches dimensional analysis, doing conversions until the resulting answer. For Example:

Order: Sulfisoxazole 0.25g po

Label: Sulfisoxazole 500mg/tab (scored)

How many tablets should be administered?

This is how I have learned to set it up:

0.25g X 1000mg X 1tab

1g 500mg

(Edited to say: this is not letting me set this up right. The 1g should be under 1000mg and the 500mg should be under the 1 tab.)

Answer is .5tablet, or ½ tablet.

How were you taught to work this problem?

Jill

2,016 Posts

Specializes in Telemetry & Obs.

I would convert the 0.25 G to mg first since that's how the med is supplied...then set it up:

500 mg/1 tab = 250 mg/X

cross multiply:

500X=250

divide both by the 500 to get the X alone:

500X/500=250/500

X=1/2 tablet

1 Article; 2,212 Posts

Specializes in critical care; community health; psych.
Hi. I have a question for all of you nursing students who have learned some clinical calculations. I am wondering what method you were taught for solving the problems? I am starting nursing school in August and have been reading Clinical Calculations A Unified Approach by Daniels and Smith. This book teaches dimensional analysis, doing conversions until the resulting answer. For Example:

Order: Sulfisoxazole 0.25g po

Label: Sulfisoxazole 500mg/tab (scored)

How many tablets should be administered?

This is how I have learned to set it up:

0.25g X 1000mg X 1tab

1g 500mg

(Edited to say: this is not letting me set this up right. The 1g should be under 1000mg and the 500mg should be under the 1 tab.)

Answer is .5tablet, or ½ tablet.

How were you taught to work this problem?

Jill

I prefer the dimensional analysis method over the ratio method. We were taught the ratio method but a friend taught me DA. I prefer it because every problem is set up exactly the same way. No memorization of different formulas. I like that all you have to remember is basic conversions and to start off with what you want.

I set it up slightly different sort of reversing the order beginning with the unit you want:

You want # of tabs, so:

Tabs = 1 tab x 1000 mg x 0.25 g

500 mg x 1 g x dose

It's just a little bit of a reverse order

Edited to say that I see you tried to set it up this way but couldn't. It appears I couldn't do it either.

24 Posts

Hi. I have a question for all of you nursing students who have learned some clinical calculations. I am wondering what method you were taught for solving the problems? I am starting nursing school in August and have been reading Clinical Calculations A Unified Approach by Daniels and Smith. This book teaches dimensional analysis, doing conversions until the resulting answer. For Example:

Order: Sulfisoxazole 0.25g po

Label: Sulfisoxazole 500mg/tab (scored)

How many tablets should be administered?

This is how I have learned to set it up:

0.25g X 1000mg X 1tab

1g 500mg

(Edited to say: this is not letting me set this up right. The 1g should be under 1000mg and the 500mg should be under the 1 tab.)

Answer is .5tablet, or ½ tablet.

How were you taught to work this problem?

Jill

I ALWAYS had problems doing the math calculations UNTIL I learned Dimensional Analysis now it is actually easy and fun to figure the math.

NEED = 0.25 g

HAVE = 500 mg/tab

What you want to know = # of Tabs

Tabs = 1 Tab/500 mg X 1000 mg /1g X 0.25 g = 250/500 = 0.5 tabs

:)

717 Posts

Specializes in ER.

I am also a big fan of dimensional analysis......you can figure out anything with that, once you get the hang of it!

33,512 Posts

Specializes in Med-Surg, Trauma, Ortho, Neuro, Cardiac.

I would have done it similar to above, convert the ordered .25g into mg since that is how the tablit is supplied. .25 = 250 mg. Then in my head I would have seen 250 mg is going to half of a 500 mg tablet.

On paper it would have looked liked:

xtab/250 mg = 1 tab/500mg and cross multiplied to find out the x = .5

739 Posts

Specializes in OBGYN, Neonatal.

DA all the way! Dimensional Analysis.

819 Posts

Specializes in Med-Surg.

What a wonderful self-motivated go getter you are OP !! Way to get ahead of the game! ; )

I took a dose math class for nurses and we were taught to do the problem exactly the way you had it set up. Dimensional analysis is definitely the way to go. (Also comes in very handy for all the math in General Chem!)

BTW, If you haven't checked your box yet, there's a wicked-long e-mail in there from me!

178 Posts

i use the formula: D (doctor order) x Q [quality]

---

H (have)

so it would be 0.25g x tabs

--------

500mg

1g=1000mg therefore 0.25g is 250mg. just move backwards 3places

and solve... 250mg

---- x tab

500mg

cross out the zeros and mg left with

25 5 1

---- = ----- = ----- = and divide....

50 10 2

121 Posts

What a wonderful self-motivated go getter you are OP !! Way to get ahead of the game! ; )

Thank you, MD, for bringing to my attention why it is I am studying during my last free summer! I am a go-go-getter! I just hope I am getting it the way I will be taught. There's nothing like teaching yourself something and then having your professor muck it up and teach you the 'right' way.

Thanks for all of the input, everybody. I really appreciate it.

Jill

168 Posts

i use the formula: D (doctor order) x Q [quality]

---

H (have)

so it would be 0.25g x tabs

--------

500mg

1g=1000mg therefore 0.25g is 250mg. just move backwards 3places

and solve... 250mg

---- x tab

500mg

cross out the zeros and mg left with

25 5 1

---- = ----- = ----- = and divide....

50 10 2

I also do it in a similiar way:

D (desired) divide by H (have) then multiply V (vehicle, ex: tab)

(D/H) x V

so (250 mg / 500 mg) x 1 tab = 1/2 tab

2,029 Posts

Specializes in PICU, Peds Ambulatory, Peds LTC.

This is how I learned it:

D.O. 0.25 g P.O

Available: 500 mg/tab Scored

First of all you have to change the Dr. Order from grams to milligrams, because what's available is in mg not grams.

1 g = 1000 mg {I use the decimal change}

Therefore, 0.25 = 250 mg

This is the set-up I alway's use:

250 mg

------- x 1 tab = x tab

500 mg

{Cancel off the 0}

Then divide:

250

---- x=

500

x= 0.5 tab. Remeber to change it to 1/2 tab.

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