How were you taught to solve this medication calculation problem?

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?
Thank you for your time!
JillLast edit by Jill1215 on Jun 28, '04 

Jun 28, '04Occupation: Obs Unit Specialty: Telemetry & Obs ; From: US ; Joined: Oct '03; Posts: 2,412; Likes: 1,820I 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 
Jun 28, '04Occupation: Nurse, of course Specialty: critical care; community health; psych ; Joined: Sep '03; Posts: 2,355; Likes: 621Quote from Jill1215I 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.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?
Thank you for your time!
Jill
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. 
Jun 28, '04Joined: May '04; Posts: 24; Likes: 6Quote from Jill1215I ALWAYS had problems doing the math calculations UNTIL I learned Dimensional Analysis now it is actually easy and fun to figure the math.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?
Thank you for your time!
Jill
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 
Jun 28, '04Specialty: ER ; Joined: Apr '03; Posts: 806; Likes: 93I am also a big fan of dimensional analysis......you can figure out anything with that, once you get the hang of it!

Jun 28, '04Joined: Oct '02; Posts: 60,456; Likes: 16,891I 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 
Jun 28, '04Occupation: RN (OBGYN) Specialty: OBGYN, Neonatal ; Joined: Jun '04; Posts: 728; Likes: 58DA all the way! Dimensional Analysis.

Jun 30, '04Occupation: RN Specialty: 3 year(s) of experience in MedSurg ; Joined: May '04; Posts: 826; Likes: 47What a wonderful selfmotivated 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 wickedlong email in there from me! 
Jun 30, '04Joined: Jun '04; Posts: 178; Likes: 17i 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 
Jun 30, '04Joined: May '04; Posts: 138; Likes: 5[QUOTE=mariedoreen]What a wonderful selfmotivated 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 gogogetter! 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 
Jun 30, '04Joined: Mar '04; Posts: 226; Likes: 3Quote from janetretteI also do it in a similiar way: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
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 
Jun 30, '04Occupation: PICU Nurse Specialty: 7 year(s) of experience in PICU, Peds Ambulatory, Peds LTC ; From: US ; Joined: May '04; Posts: 5,266; Likes: 24This 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 setup 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 
Jul 1, '04Joined: May '04; Posts: 111)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)