# drug calculations

Posted
BWORN (New)

I need some help w/drug calculations! Can someone show me how to do the following?

Dopamine 500 mg/500 ml to run at 5mcq/kg/min. Pt wt is 80kg. What would the flow rate in ml be?

Dopamine 500 mg/500 ml to run at 5mcq/kg/min. Pt wt is 80kg

That's a weird Dopamine mix. Ours is normally 400mg/250ml or 800mg/250ml.

But to answer your question you take 500mg/500ml to get mg/ml. Then divided it by 60 to get mg/ml/min. Then multiply it by 80kg to get mcg/ml/min. That number you divide by 5mcg/kg/min to get you drip rate.

500/500 x 1000, divide answer by 60, then--divide by 80, gives you a constant(K=0.208) 5mcg divided by constant = 24.038 cc or 24cc/hr. Thats how I do it.

Thanks! I may be dense or a little sleep deprived but the ratio is 1:1 divided by 60 is .02 X 80 Kg = 1.6 divided by 5mcq/kg/min =.32 X 60 = 19.2....is that correct?

Specializes in Everything except surgery. Has 27 years experience.

Here is how I did it.

500/500= concentrations 1000 mcg/ml 80kg x 5mcg/kg/min =400 mcg/min 400/1000 = 0.4mcg x 60 min= 24micro gtts/min or on a pump 24 ml/hr right???

Thanks Brownie! I've always used the computer to figure out the drip rates for different drugs. I've forgotten how to set up the formulas. I want to thank everyone who's responded to my question.

Bworn

Specializes in Everything except surgery. Has 27 years experience.

You're very welcome BWORN ! I wouldn't have remember either if I hadn't been taking the dreaded drug tests to work agency..UGH!

Doing the happy dance!

Just had our final today in Pharmacology I - Calculations and aced it! The 100 I made on the final gives me a 97 for the course

I know that Calc is the easy part but still I take the lil' victories as they come!

Now . . . . If I can just do as well in Pharmacology II . . . . . .

Specializes in Everything except surgery. Has 27 years experience.

good luck!

bedpan, congratulations!!!!!!!!!

Thanx Brownms46 and guru

Specializes in Emergency, Trauma. Has 8 years experience.

All mcg/kg/min gtts can be calculated using the same formula- I write this down for every new nurse I precept to stick to the back of their badge for easy reference.

MG of drug x 1000=

Divided by amt of fld=

divided by 60 (min)=

divided by kg weight= DF(your dosage factor)

mcg/kg/min divided by DF=cc/hr

Be sure to write down your dosage factor, so that when you need to titrate, you don't have to repeat all the steps.

To see this in action:

I have 400 mg of Dopamine in 250 cc NS. I want to start my drip at 10 mcg/kg/min. My pt weighs 70 kg.

400mg x 1000= 400,000

400,000 divided by 250 cc= 1600

1600 divide by 60 minutes= 26.7

26.7 divided by 70 kg = 0.38 (DF)

10 (mcg/kg/min) divided by 0.38 (DF) = 26 cc/hr

Now let's say I want to titrate that same drip up to 15mcg/kg/min, I would simply plug my DF into the last equation (mcg/kg/min divided by DF = cc/hr)

15 divided by 0.38 = 39 cc/hr.

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