Medical dosage questions

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I have 2 questions that I can't figure out. Here is the first one and my attempt at it:

Order 50mcg/kg/min. Label states 1mL=0.25 mg. How many mL is needed for this order?

50mcg x 1mg x 1ml

1000 mcg 0.25mg = 5mL ? feel like I am missing something?

Then this one I have no clue how to attempt but here is what i put down seems like it's too long to me

Order 4 mcg/kg/min, IV bag has 800mg of Dopamine in 500mL of D5W. Patient weighs 70kg. Drop factor is 10drops=1mL. What is the flow rate in drops per hour?

70kg x 4mcg x 1mg x 60min x 500ml

kg/min 1000mcg 1Hr 800mg =

thanks

Specializes in PICU, Sedation/Radiology, PACU.

The first one is not correct. What makes it tricky is the units. Make sure you convert everything to one unit and provide your answer in the appropriate units.

First, figure out how many micrograms there are in 0.25 mg. Remember that one milligram is equal to 1,000 micrograms.

Then use your dosage calculation formula to find out how many mL's you need if you need 50 mcg and you have X number of micrograms in 1 mL.

So what's your new answer?

In the second problem, I find it easier to break these problems down into steps rather than plugging everything into one formula. It's easier when you understand the process instead of trying to figure out where the numbers go. This one is a little more complicated, so I'll talk you through it.

First, you again have to convert everything to one unit. So if you have 800 mg and 1 mg is 1000 mcg then that means your 500mL bag of Dopamine contains 800 X 1000 = 800,000 mcg of dopamine.

Now you want to know how many mcgs are in one mL of your solution. To do this, divide the total amount of the medication by the total volume in the bag. 800,000 mcg / 500 mL = 1,600 mcg/mL of dopamine.

Then, figure out what dose of the medication you want to give. Your dose is in mcg/kg/min so to find out how much medication need for one minute, multiply the ordered amount by the patient's weight. 4mcg x 70 kg = 280 mcg of dopamine per minute.

Since your question wants the flow rate in drops per hour, you need to find out how many mcgs you need to give in one hour. Since you know how many you need per minute, multiply that by 60 in order to get the amount you're giving over one hour. 280 mcg/min x 60 min/hr = 16,800 mcg/hour

Now you can use your formula to figure out how many mLs you will be giving in one minute. You need 16,800 nag per hour, and your bag contains 1,600 mcg/mL. So simply divide your desires dose by the amount you have on hand, and multiply by the volume . 16,800 mcg / 1600 mcg x 1 mL (because there are 1,600 mcg/mL) = 10.5 mL of medication per hour.

Now, for the drip rate. Your tubing is 10 drops per mL. You need to give 10.5 mL in one hour. So multiply your drops/mL times your mL/hr to get your drip rate. 10 drops/mL x 10.5 mL/hour = 105 drops per hour.

Don't forget that in any medication problem, you need to first convert the dosages to the same unit. Your answers will be the same as long as you use the same unit- it doesn't matter if you convert everything to mg or to mcg. You can't solve a problem when you're working with two different units.

It looks to me like you set-up the first one correctly, but because AllNurses formatting shifts things when you actually post, it's hard to tell.

To me, it looks like you DID try to convert to to the same units (milligrams) by multiplying 50 mcg per kg per minute TIMES (1mg/1,000 mcg)

It also looks like you correctly were going to then multiply by (1mL/0.25 mg) so you should have the following:

(50 mcg per kg per minute x 1 mg x 1 mL) DIVIDED by (1,000 mcg x 0.25 mg) = answer in milliliters per kg per min

[milligrams and micrograms on the top and bottom cancel out leaving only milliliters per kg per min]. If it was just strange AllNurses formatting and that IS how your problem was set-up, I'm not sure how you ended up with an incorrect answer of 5 mL

Does your patient weigh 25 kg??

On the second one, it looks like you were just missing your conversion factor from milliliters to drops, that is, you need to add:

10 gtt

x ---------

1 mL

or...

MULTIPLY by 10 gtt / 1 mL

OK answer is 0.2 right? Thanks soooooo much IndyElmer, I multiplied wrong..

Ashley Thanks so much, I get it now !!!!!!!!

OK answer is 0.2 right? Thanks soooooo much IndyElmer, I multiplied wrong..

That's what I got (but I'm relatively new to this :) )

0.2 what? I got 0.2 mL per kg per min

Specializes in Acute Care, Rehab, Palliative.

You can't get answer for the first one because it doesn't tell you what the pt weighs and the dose is mcgs /kg. Kg is a unit of weight.

Specializes in Critical Care, ED, Cath lab, CTPAC,Trauma.

there are certain essential parts to every equation.......

desired dose:

concentration:

volume on hand:

lb to kg:

looking for:

administration set up:

any conversions necessary?

your first question if the patient is 1kg. if the patient weighs more than 1kg you would have to multiply by the kilogram in weight.

order 50 mcg/kg/min. label states 1 ml=0.25 mg. how many ml is needed for this order?

desired dose: 50 mcg/kg/min

concentration: 0.25mg/ml

volume on hand: 1ml

lb to kg: n/a

looking for: mcg/kg/min

administration set up:n/a

any conversions necessary? yes

desired dose x volume on hand

concentration = ml to be given

50mcg/kg/min x 1ml

0.25mg which is how many mcg?(1mg=1000mcg)

50mcg/kg/min x 1ml

250 mcg = how many mcg/kg/min

then take that answer x the kg in weight to get mcg/kg

the next problem the same set up

order 4 mcg/kg/min, iv bag has 800mg of dopamine in 500 ml of d5w. patient weighs 70kg. drop factor is 10drops=1 ml. what is the flow rate in drops per hour?

desired dose: 4 mcg/kg/min

concentration: 800mg

volume on hand: 500ml

lb to kg: 70kg

looking for: 4 mcg/kg/min

administration set up: 10drops=1 ml

any conversions necessary? yes

desired dose x volume on hand

concentration = ml to be given

first how many mcg/ml of dopamine

mcg x 500

800mg (how many mcg's if 1mg=1000mcg) 800 x 1000 =800,000

so

1 x 800,000mcg

500 = ? (1600mcg/ml)

so you know that you have 1600mcg (of dopamine) per 1ml

desired dose x volume on hand

concentration = ml to be given

4mcg/kg/is the desired dose how many kilograms is the patient

4mcg x 70kg = 280 mcg/min

you need to gtts per hour

280mcg/min x 60 min = 16800mcg/hr

16800 mcg/hr x 1ml

1600mcg = 10.5 ml/hr

if you need 10.5ml/hr and your tubing takes 10 ggt/min to equal 1ml

10.5 ml x 10 gtts

1ml = 105 gtts/hr.

i have given you site in the past please look at them they will help you alot!!!!

http://www.dosagehelp.com/

[color=#660099]drug dose calculations - dave's ems

"order 50mcg/kg/min. label states 1ml=0.25 mg. how many ml is needed for this order?

50mcg x 1mg x 1ml

1000 mcg 0.25mg = 5ml ? feel like i am missing something?"

yes, you are missing the weight of the patient. you can't give mcg/kg/min without knowing the kg part.

think about it. i will give you, say, two mcg of chocolate per kilogram of your weight every minute-- 2 mcg/kg/minute. how many micrograms of chocolate is that in an hour? say you weigh 70kg. therefore, i have to give you 140 mcg every minute, x60 is how many mcg in an hour. mmm. if you sit down and try to sketch it out, sometimes the way to figure out the answer is clearer.

"order 50mcg/kg/min. label states 1ml=0.25 mg. how many ml is needed for this order?

50mcg x 1mg x 1ml

1000 mcg 0.25mg = 5ml ? feel like i am missing something?"

yes, you are missing the weight of the patient. you can't give mcg/kg/min without knowing the kg part.

you have already been told the mcg/kg/min and you can easily calculate the ml/kg/min without patient weight.

if the question is asking you to calculate the rate in ml/min or ml/hr, then yes, you need the patient's weight.

if the question is asking you to calculate the total volume you need (ml), then you need to know more than just the additional factor of the patient's weight. you also need to know the duration of the administration time.

unfortunately, the question as typed in the original post appears to either be missing info (patient weight and administration duration) or the question didn't really ask "how many ml is needed for this order?"

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