Please Help!!! a Med/Admin Question??

[mad9]

Ok So this is one of my best courses however I am struggling with finding the correct formula : Desired Dose/ Dose on Hand multiplied by Drug Factor or DD/DOH X DF= answer. for reconsitution of Powered Drugs.

Here is what I mean:

a) The doctor orders Cloxacillin sodium 0.175 g IM q6h. The medication is available in a 5oomg vial. Instructions are to add 1.7ml of sterile water to yeild 2mL. How many mL(s) should be administered for one dose?

I know what the doctor orders is the desired dose (0.175 g) and I think that the 500 mg is the dose on hand and the drug factor is 2 mL?

So my equation should read: DD=0.175 g/DoH=500mg x 2mL

I also have to convert the DoH of 500 mg to g, right?

Also 1000 mg = 1 g correct?

Do I have this correct?

Please help. Thank you

MD9

[mad9]

I got it!

DD=175 g/DoH=5 g x 2 mL = 0.7 mL

:)

[Daytonite, BSN, RN]

you will find many examples of this type of problem worked out on this thread which is on this forum. it has a sticky on it so it appears in a list at the top of the forum when you first pull up the list of threads:

https://allnurses.com/forums/f205/dosage-calculations-88867.html

to set this problem up and work it out by dimensional analysis (factor label) method it would look like this. you want to end up with the label of ml:

0.175 gram

/

1

(dose desired)

x

2 ml

/

500 mg

(dose on hand)

x

1000 mg

/

1 gram

(conversion factor)

=

0.7 ml

(after doing the math and canceling out duplicate labels in the numerators and denominators)

when i set up these problems i do not consider a separate drug factor. i consider the dose on hand to be 500 mg/2 ml of solution. since this fraction becomes the term in the denominator of the dose desired divided by the dose on hand formula, you end up with a complex fraction--a fraction that has a fraction in the denominator. in order to clear a fraction from the denominator you need to multiply both the numerator and denominator of a term by the reciprocal of the fraction in the denominator in order to make the denominator equal the number 1. in so doing, you end up with the multiplication problem above, where the dose on hand fraction is now flipped over, with a conversion factor applied in order to cancel out labels and end up with the final label of ml on the final mathematical solution.