Help with Dosage Calculations

NursingStudent27 · Oct 15, 2008

Hi, hopefully I can help a little bit with dosage calculation. I however, cannot help with the IV drip rates because I haven't quite figured that part out yet. Unfortunatly, at the LPN school that I attend they tried to teach us the Math part in one day and then tested us over it....that didn't go over so well to say the least. Anyways, I'll help all I can. I will give you an example off of one of my practice sheets.

Order: Benadryl (diphenhydramine) 25mg, PO, q6h, PRN

Available: Benadryl 12.5mg/5mL

First step: You need to divide what you need and what you have. What you need is the top number and what you have is the bottom number.

25mg (what you need)

-----------------------

12.5mg (what you have available)

Whatever answer you get from that you will multiply it by the volume.

25mg

------- x 5mL = 10mL

12.5mL

So, with this one your answer would be 10mL q6h, PRN

If you need anymore help let me know. Do you know how to convert grams to milligrams? If you don't or need help just private message me!! We can learn together.

Silverdragon102, BSN · Oct 15, 2008

Check out the student forums as there are a couple of posts/threads on maths

ericnli · Oct 16, 2008

Hey...

.. I hope my answer will help you a little.

Having iv amount ( 1000ml ) run for 8 h

=

Devide amount by hours ( 1000 : 8 = 125 )

Devide that by 60, for 60 min. ( 125 : 60 = 2.083333 )

Time this the drops per mil. as described in the question, for example 15 drops per mil.

( 2.083333 x 15 = 31.25 )

That should be your answer.

If you have an amount of medication and need to figure out the ml count down to 1 ml.

( order is 125 mg of a medication and the pharmacy mixes it 2500 mg in 100 ml )

2500 : 100 = 25 (= 25mg medication per ml )

Devide the amount ordered by the result.

125 : 25 = 5

Meaning that 5 ml need to be administered.

I have used that way and got good 99% and all the Dosage Questions.

Hope it helps.. :wink2:

michelle meeks · Oct 16, 2008

Thanks a lot!!! nursing student 27.

This was helpful...

A2008 · Oct 16, 2008

Total volume(TV) x Drop Factor (DF)

________________________ = gtts/min

Time (in minutes)

Total volume, drop factor and time are usually given in the problem. DF is usually 15 or 60. To calculate time in minutes, just take the number of hours and convert into minutes (60 min in each hour) 3hours = 60x3=180 min

The order that you do everything is important. First multiply the top two numbers and get your answer. Then divide that answer by the time.