Confused! Dosage calculations

nursebride2012 · May 10, 2013

All you need to do is multiply 60 by 20 is 1200 and divide by 90 and your answer is 13.333333 rounded is 13gtt/min

lclopez86 · May 10, 2013

thank you for your help

Esme12, ASN, BSN, RN · May 10, 2013

nice job on a long problem.....:) however....you ordered dose daily:

This patient weighs 82.73kg x 200mg/kg/day= 16546mg/day.

Order is for q4h: that's 6 doses. 16546mg/6 doses= 2757mg per dose...so recalculate

Madras · May 10, 2013

Hi, I'm just a student myself so anyone correct me if I'm wrong....

To get the ordered dose daily:

Pt weighs 82.73kg x 200mg/kg/day= 16546mg/day.

Order is for q4h: that's 6 doses. 16546mg/6 doses= 2757mg per dose.

You have Retrovir 3000mg/12ml equivalent to 250mg/ml

2757mg/ 250mg= 11.028ml is what would be added into the 48ml of LR so approx 60mL of LR to be infused over 90 minutes.

So you've got 60ml/90 minutes= 0.6666666667 x20gtts/min= 13.33 round to 13gtts/min

:banghead:

AmberHopefulRN · May 10, 2013

Q4hrs therefore give 6 doses in one day
(16,545.45 mg/day) X (6 doses/1 day) = 99272. 73 mg/dose

Shouldn't this be (16,545.45 mg/day) / (6 doses/1 day) = 2757.58 mg/dose?

The way I am reading it here, you would be giving 595,636.38 mg per day to the patient. Or am I missing something?

lclopez86 · May 10, 2013

you're right, instead of dividing, I multiplied. thank you for catching my error!

nurseprnRN, BSN, RN · May 10, 2013

I'm having difficulties completing this problem.
Ordered: Retrovir 200 mg/kg/Day IV q4 hr in 60 mL LR over 90 mins.
On Hand: Retrovir 3 g vials. Each gram is reconstituted with 4 mL of diluent
patient weighs 182 lb. Use macrotubing 20 gtt/mL
Dilute the reconstituted Retrovir in 48 mL of LR
calculate flow rate:
I know the formula is:
I'm having troubles differentiating what is "filler" and what is not.
So far I have:
Convert lbs to Kg
182 lbs (1 kg/2.2 lbs) = 182/ 2.2= 82.73 kg
Find ordered dose in mg/day
200mg/kg/day
(200mg/kg/day) X 82.73 kg = 16,545.45 mg/day
You're perfect to here. Good thinking.
Find ordered dose in mg/dose
Q4hrs therefore give 6 doses in one day
(16,545.45 mg/day) X (6 doses/1 day) = 99272. 73 mg/dose
Um, no. That's a dose for the whole day, so for six doses you'd divide that by six. Look at what you have. You've determined that you're going to give 16,545.45 mg/day...so why would ONE dose be a whole lot bigger than that?
Find concentration of medication on hand:
3 g is 3000 mg
Each gram is reconstituted in 4 mL
3000 mg/12 mL = 250 mg/mL

So one dose is 2757mg. Now you should be able to figure how many reconstituted cc of the med will go in the minibag to make a total of 60cc, and then you can figure out how fast to run it.

Tinker88 · May 10, 2013

Ok I get it now too! LOL

EaglesWings21, ASN, RN · May 11, 2013

I would try to look up how to do dimensional analysis. It really helped me with dosage calculation and I got a 100% on my test this past semester. This website has a powerpoint that shows you how to do it:

Dosage Calculation Using Dimensional Ana

lrbersamina · May 14, 2013

Great post on dosage calc help! The site is very helpful thank you.

Esme12, ASN, BSN, RN · May 14, 2013

We try! :)