sources for learning dosage calculations

ladynurse1 · Apr 18, 2009

Study ratio and proportions. Mostly all calculations can be solved by ratio and proportions. The textbook that we used for our class is Drug Calculations: Process and Problems for Clinical Practice by Brown Mulholland 8th edition and it breaks it down step by step.

NamasteNurse, BSN, RN · Apr 18, 2009

Easy peasy. Desire over have equals dosage. The order says 250mg of tylenol, you have on hand 500mgs. Divide 250 divided by 500. The dose to give is 0.5. There are lots of great posts and links on this site, do a search and don't fret. Practice a lot though cause some people just don't get it.

LaneRN · May 4, 2009

If you still need help I have sme notes I can send you just send me a message

nlion87 · May 4, 2009

Attached is a link to our pharmocalogy math text book used in my program which is available at amazon.com (used are available). A geat resource and made easy in terms of understanding dimensional analysis, which is th cornerstone of pharmacology. I strongly urge you obtain it if you have the financial means. As I stated above, used copies are available. Well worth the investment in my opinion. Hope this helps

Dimensional Analysis for Meds (Paperback)

by Anna M Curren

tsprague · May 4, 2009

could you please send me the notes you are talking about.

[email protected].

thanks

tnlpn8 · May 4, 2009

Oh that would be Great! that is very sweet of you! My e-mail is [email protected]. Thanks again I really do appreciate you taking the time, let me know if there is anything I can do for you!

Melissa

LaneRN · May 5, 2009

I have emailed the two members above the notes figured I would just attach them here so anyone who wants to can have them. They helped us all alot with all of our problems these are all formulas.

Math Tips 4-083.doc

Math Tips 4-08 nursing dosage caculations2.doc

tnlpn8 · May 5, 2009

I was unable to open the attachment, but thanks so much any way! :)

LaneRN · May 6, 2009

Being that some can not open the attachments for the drug caculations tips above I am just going to copy it here

Math Tips

Calculating drops/minute

Multiply the mL to be infused by the drop factor of the tubing and divide by the number of minutes over which you are infusing the fluid.

x gtts/mL=gtts/minute

So, if you have 1000 mL to infuse in 6 hours and the gtt factor for the tubing is 15 gtts per mL:

x 15= 41.6 or 42 gtts/minute

Calculating the flow rate for an intermittent infusion like a minibag

Figure out what portion of an hour your infusion time is: ie, 30 minutes is ½ of an hour; 20 minutes is 1/3 of an hour; 15 minutes is ¼ of an hour…..etc.

Multiply the volume of fluid by the bottom number of the fraction. This will give you the rate of infusion for that amount of fluid.

Examples:

1. You have Rocephin 1 gram in 100 mL NS to run over 30 minutes. The volume is 100 mL.

30 minutes is ½ of an hour.

Multiply 100 by 2=200.

You would set the infusion pump at 200 mL/hr.

2. You have Rocephin 1 gram in 100 mL NS to run over 20 minutes.

The volume is 100 mL.

20 minutes is ¼ of an hour.

Multiply 100 by 4=400.

You would set the infusion pump at 400 mL/hr.

3. You have Rocephin 500 mg in 50 mL NS to run over 30 minutes.

The volume is 50 mL.

30 minutes is 1/2 of an hour.

Multiply 50 by 2 = 100.

You would set the infusion pump at 100 mL/hr.

LaneRN · May 6, 2009

here are a few more notes for those who want them

calculating volume of a suspension or oral liquid medication:

desired amount in mg (or other measurement) x ml = ml/dose

amount on hand in mg (or other measurement)

example:

order: prednisone 9 mg po. on hand, you have prednisone 15 mg/5 ml.

9 x 5 = 3 ml/ dose

15

1. answers with "dangling "decimals will be graded wrong. example- .5mg is incorrect, the correct answer is 0.5mg

2. answers with a zero placed behind a decimal will be graded wrong example: 5.0 mg is incorrect the correct answer is 5 mg

3. the correct rounding procedure is as follows:

a. if a number is less than 1 ml, round to the nearest tenth place

example- 1.68 ml is rounded to 1.7 ml

1.64 is rounded to 1.6

4. when solving an iv rate calculation, the gtts/hr must be rounded to a whole number

example: 20.83 gtts/hr is rounded to 21 gtts/hr

20.1 gtts/hr is rounded to 20 gtts/hr

20.7gtts/hr is rounded to 21 gtts/hr

5.when solving an iv rate calculation, the ml/hr must be rounded to a whole number

example: 120.83 ml/hr is rounded to 121 ml/hr

20.1 ml/hr is rounded to 20 ml/hr

20.7 ml/hr is rounded to 21 ml/hr