sources for learning dosage calculations


Apr 18, '09From: US ; Joined: May '08; Posts: 206; Likes: 54Study 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.

Apr 18, '09Occupation: admin Specialty: 8 year(s) of experience in pediatrics, geriatrics, LTC ; From: UK ; Joined: Dec '08; Posts: 689; Likes: 719Easy 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.

May 3, '09Occupation: RN Specialty: geriatrics ; From: NC ; Joined: May '07; Posts: 220; Likes: 73If you still need help I have sme notes I can send you just send me a message

May 4, '09Joined: Apr '06; Posts: 251; Likes: 86Attached 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 

May 4, '09Joined: Feb '09; Posts: 18; Likes: 4Oh that would be Great! that is very sweet of you! My email is jjungle@cableone.net. Thanks again I really do appreciate you taking the time, let me know if there is anything I can do for you!
Melissa 
May 4, '09Occupation: RN Specialty: geriatrics ; From: NC ; Joined: May '07; Posts: 220; Likes: 73I 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 4083.doc
Math Tips 408 nursing dosage caculations2.doc 
May 5, '09Joined: Feb '09; Posts: 18; Likes: 4I was unable to open the attachment, but thanks so much any way!

May 5, '09Occupation: RN Specialty: geriatrics ; From: NC ; Joined: May '07; Posts: 220; Likes: 73Being that some can not open the attachments for the drug caculations tips above I am just going to copy it here
Calculating drops/minuteMath Tips
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[FONT=Cambria Math]
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[FONT=Cambria Math]
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.
Last edit by LaneRN on May 5, '09 : Reason: format incorrect 
May 5, '09Occupation: RN Specialty: geriatrics ; From: NC ; Joined: May '07; Posts: 220; Likes: 73here 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