How were you taught to solve this medication calculation problem?

  1. 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 tablet.

    How were you taught to work this problem?

    Thank you for your time!

    Jill
    Last edit by Jill1215 on Jun 28, '04
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  2. 12 Comments

  3. by   truern
    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
  4. by   wonderbee
    Quote from Jill1215
    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 tablet.

    How were you taught to work this problem?

    Thank you for your time!

    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

    Answer: 0.5 tabs

    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.
  5. by   dhudzinski
    Quote from Jill1215
    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 tablet.

    How were you taught to work this problem?

    Thank you for your time!

    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
    Last edit by dhudzinski on Jun 28, '04 : Reason: Formating lost in translation
  6. by   LeesieBug
    I am also a big fan of dimensional analysis......you can figure out anything with that, once you get the hang of it!
  7. by   Tweety
    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
  8. by   cherokeesummer
    DA all the way! Dimensional Analysis.
  9. by   mariedoreen
    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!
  10. by   janetrette
    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
  11. by   Jill1215
    [QUOTE=mariedoreen]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
  12. by   lovinghands
    Quote from janetrette
    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
  13. by   Ari RN
    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.
    Last edit by Ari RN on Jun 30, '04
  14. by   4myfam
    1)xtabs is what your looking for so you set up a fraction with what your looking for always in the numerator (capsules, ml, etc) and the strenght in the denominator(500mg)

    2)in the second fraction convert the mg to grams in the with what ever metric unit is in the first denominator (mg) to your second numerator and what ever your converting to in the denominator (g)

    3)in the last fraction you should have the ordered doasge in the numerator(which is also the metric unit in the second denominator) over one


    xtab = 1tab x 1000mg x 0.25g
    _____ ______ ______
    500 mg 1g 1
    you'll know if you have the information correct if mg cancel mg and g cancel g and your left with your x ( which is tabs)

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