# Dosage Calculation

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by brittanyyl (New Member)

421 Visitors; 1 Post

I received practice questions over the summer for my upcoming dosage calculations test. We also received an answer sheet, but I need help figuring out how to get the answer. The problem is:

A 4 year old child who weighs 24 kg is to receive 180 mcg of digoxin PO q12h. The digoxin elixir is available in a liquid concentration of 0.05 mg/ml. How many ml should the nurse give for the dose?

If anyone would be willing to show how to set up the equation I would really appreciate it.

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KeeperMom has 10 years experience and works as a CRNP.

8,847 Visitors; 639 Posts

First, you have to determine what the question is asking and what info in the sentence is unnecessary. Second, you have to make any necessary conversions so that what is ordered and what is available are the same.

Then, all you have to do is set up the problem and solve. Do you have a drug calculation book?

There are several ways to set this problem up and you will need to figure out which one is the best method for you.

For me, it is the following formula:

D

--- x V

H

D = the drug or what is ordered

H = HAVE - what you have on hand

V = vehicle - HOW you have the drug.

so, D divided by the H, times the V

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1,821 Visitors; 54 Posts

While I'm new to all of this nursing math stuff, it would appear to me that you have a couple of things to look at.

First, what is the really important information, versus the "fluff". The impt. stuff would be "receive 180 mcg" and "(available in) 0.05 mg/ml".

Second, since mcg and mg are different units of measurement, you'd probably want to convert one to the other. In other words, convert 180 mcg into mg.

Third, figure out how many ml it will take to deliver the equivalent of 180 mcg.

Like I said, I'm new at all of this, so take it with a grain of salt. Hopefully someone who's not a brand new NS will be able to give you the "official way". That's just how I'd approach the problem...

Good luck!

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2,924 Visitors; 127 Posts

Ignore the child's weight as the problem does not say PER KG so it is fluff as stated by tcgirl.

You are looking to find out how many mls=180mcg

180mcg x 1ml/0.05mg x 1mg/1000mcg

Cancel mcg and mg and mls remain...answer=3.6mls contains 180mcg

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BacktotheBeach has 4 years experience.

9,791 Visitors; 497 Posts

I like ratio and proportion, try my fav website for help. It gives step by step instructions http://www.dosagehelp.com/

0.05 mg/1 ml = 180 mcg/x ml

change 180 mcg to 0.18 mg

then multiply

you get 0.18/ 0.05 = 3.6 ml is what the nurse should give the patient

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Mandychelle79 has 2 years experience and works as a Psych Nurse.

9,143 Visitors; 771 Posts

our program requires the use of dimensional analysis so you may want to check with your instructor.

For this problem I would do

180 mcg x 1mg/1000mcg x 1ml/.05mg = 3.6 mL

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mattfd37 has 5 years experience and works as a School & ER RN.

4,272 Visitors; 162 Posts

Whats ordered over Whats on hand times What the drug comes in. Remember, if you're going smaller (mcg) to Larger (mg) just move 3 decimal places to the Left.. 180 is now .18. Oppisite obviously if you're going bigger to smaller.