For example: The doctor orders 400mg of Advil PRN (as needed). You have 200mg tablets on hand. How many tablets will you give?
I know one could easily look at this and say 2…duh? that was easy, but this is just how it is easily figured out when working with larger #’s.
Desired= what doc orders H= what you have on hand
Set up as D/H = 400/200 = 2 tabs.
For IV’s…Just remember your calculations:
gtt(drops)/min = Volume (ml) X Drop Factor (gtt/min) / time (in minutes)
Ex: 1000mls over 10hrs = 1000 divided by 10 hrs = 100mls/hr
take 100mls and multiply it by drip factor 15gtt/ml and divide by 60 min
= 25gtt/min
Macrodrip drop factors can be 10, 15, or 20gtt/ml- this varies according to manufacturer
Macrodrip drop factor 60gtts/ml
There ya go! Sorry if this is all over the place…but math is important…I was nervous to do it at first, but if you use the simple formulas you can see it really works. Feel free to ask questions if you have any. Good luck!
Hopefully someone in your school will know dimensional analysis. You may have used it in a chemistry class. Ask around, because using that just makes sense for a lot of people, and this way you don’t have to memorize any formulas.
You do have to memorize some equivalencies though.
May 6th, 2008 at 2:03 pm
You have to be able to calculate drug dosages and also to convert units of measurements.
You have to be very careful with your math or your patient will get the wrong dosage of drug, which is very dangerous.
May 6th, 2008 at 2:07 pm
Desired over Have: Is a good way to remember it.
For example: The doctor orders 400mg of Advil PRN (as needed). You have 200mg tablets on hand. How many tablets will you give?
I know one could easily look at this and say 2…duh? that was easy, but this is just how it is easily figured out when working with larger #’s.
Desired= what doc orders H= what you have on hand
Set up as D/H = 400/200 = 2 tabs.
For IV’s…Just remember your calculations:
gtt(drops)/min = Volume (ml) X Drop Factor (gtt/min) / time (in minutes)
Ex: 1000mls over 10hrs = 1000 divided by 10 hrs = 100mls/hr
take 100mls and multiply it by drip factor 15gtt/ml and divide by 60 min
= 25gtt/min
Macrodrip drop factors can be 10, 15, or 20gtt/ml- this varies according to manufacturer
Macrodrip drop factor 60gtts/ml
There ya go! Sorry if this is all over the place…but math is important…I was nervous to do it at first, but if you use the simple formulas you can see it really works. Feel free to ask questions if you have any. Good luck!
~C
May 15th, 2008 at 7:24 pm
Yikes! I know it will all make sense eventually.
Shalom
July 25th, 2008 at 5:27 pm
Hopefully someone in your school will know dimensional analysis. You may have used it in a chemistry class. Ask around, because using that just makes sense for a lot of people, and this way you don’t have to memorize any formulas.
You do have to memorize some equivalencies though.
My golden one is
1 oz = 30 ml = 6tsp = 2 Tbs
Good Luck
July 28th, 2008 at 10:03 am
In nursing I find the most useful maths is being able to quietly count up to ten (whilst smiling at the Consultant through gritted teeth).