Pharmacology question- adding sterile water?

stelon · Sep 23, 2008

I believe the setup would be just the same as any other problem. Since your resulting solution is 1gram/2mL:

0.2 gram/1 gram x 2 mL = 0.4 mL

I just started school so if someone wants to check this, that'd be great. But I think it's right.

ICU/CCU, BSN, RN · Sep 23, 2008

I get the same answer! :yeah:

Daytonite, BSN, RN · Sep 23, 2008

the m.d. orders kanamycin 0.2 gram im q12h. the vial of kanamycin is labeled, "add 5 ml. sterile water to get a concentration of 1 gram per 2 ml." how many ml. will you give?

i like that formula too. i know it as

dose desired/dose on hand x amount the dose on hand comes in

. it's the same as your formula: order/dosage at hand x volume at hand= amount to be administered.

note that the problem tells you the final concentration after mixing the drug, so the information about adding the 5ml of sterile water isn't necessary to performing any of your calculations.

pull those terms out of the problem:

order:

0

.

2 gram

dosage at hand:

1 gram

volume at hand:

2 ml

now plug them into the formula and do the math:

0.2 gram

(order)

/1 gram

(dosage at hand)

x 2 ml

(volume at hand)

=

0.4 ml

(amount to be administered)

stelon · Sep 23, 2008

Yay. I too love using that formula. When I actually took medical math they taught us a different way that seemed a lot more difficult to me. Ever since I started using this formula, I haven't missed one. :)

cherubhipster · Sep 23, 2008

Thank you guys!! It was defintately the sterile water screwing me up. I was thinking of the part of the formula "volume on hand" in terms of the entire concetration of the bottle, not the volume on hand per unit.

My boyfriend (who isn't even a healthcare professional, just good at math) said to think of the problem as if it was tablets instead of a liquid. Just because there are 5 tablets in the bottle doesn't mean that is the number you use in the formula.

I definately like this forumla better than the long proportion forumla. Now I just have to get faster at my metric conversions...

sfranRNstudent · Oct 3, 2008

the m.d. orders kanamycin 0.2 gram im q12h. the vial of kanamycin is labeled, "add 5 ml. sterile water to get a concentration of 1 gram per 2 ml." how many ml. will you give?
i like that formula too. i know it as
dose desired/dose on hand x amount the dose on hand comes in
. it's the same as your formula: order/dosage at hand x volume at hand= amount to be administered.
note that the problem tells you the final concentration after mixing the drug, so the information about adding the 5ml of sterile water isn't necessary to performing any of your calculations.
pull those terms out of the problem:
order:
0
.
2 gram

dosage at hand:
1 gram

volume at hand:
2 ml

now plug them into the formula and do the math:
0.2 gram
(order)
/1 gram
(dosage at hand)
x 2 ml
(volume at hand)
=
0.4 ml

(amount to be administered)

now these are what my test questions are going to look like....2days after my first class i have to take a test like this. how do i prepare....do i just need to memorize the conversions, some of them i figure out and some i am lost. i still havnt gotten my books im just worrying b/c math was never my strong subject if you know what i mean

cherubhipster · Oct 3, 2008

Now these are what my test questions are going to look like....2days after my first class I have to take a test like this. How do I prepare....Do i just need to memorize the conversions, some of them I figure out and some I am lost. I still havnt gotten my books im just worrying b/c math was never my strong subject if you know what i mean

Definately memorize those conversions!!! Luckily our book is pretty good and lays them out well. I made flashcards with all the conversions and just did them over and over. You don't have to really understand how they work- just know 1 gram= 1000 milligrams, 1 gram= 1000000 micrograms, etc.

There are some threads kicking around the forum if you search for them with websites that have practice problems too. You can try that since you don't have a workbook to use. I haven't learned IV calculations yet, and a lot of them are for that, so I just skipped over those. But make sure you do lots of practice problems! Good luck!