# Meds / Math / reconstitution of powder HELP!

1. Does anyone know where to find this stuff? I don't understand how I am to determine the amount of liquid to use in reconstitution in the following problems:

The physician orders 5,000,000 U of Penicillin IV. You have a vial containing 20,000,000 U of Penicillin powder. How many ml of liquid must be added to the vial to make 5,000,000 U equivalent to 5 ml?

You have a vial of Mefoxin 1 g in powder form. You are to give 200 mg IM. How much diluent will you add, and how many ml will you give?

Joined: Aug '02; Posts: 1,062; Likes: 7
RN, ICU/CCU

3. ratio and proportion

5,000,000 U = 20,000,000 U
5 mL .................... x mL

then cross multiply

5,000,000 x = 100,000,000

x = 20 mL

you should add 20 mL of dilutent to make each 5 mL equal 5,000,000 U

hmmm........er........i think

the second one doesn't hit me at the moment. it seems like something is missing but i'll give it a shot too.

1 g = 1000 mg (this is fact)

if you give 200 mg in only 1 mL

then you would have to add 5 mL dilutent

200 mg = 1,000 mg
1 mL.............x mL

then cross multiply

1,000 = 200 x

5 mL = x

but the only way i came up with that is too assume that you are going to give a certain amount.

not sure about either of these either. in real life i would call pharmacy :chuckle
4. THANK YOU SO MUCH! I just could not grasp that. I figured it would be easy and make me look bad LOL!!!

I have the answers, as these are practice questions and you are right on the first one. The 2nd one has 5 different answers depending on the diluent. What a mess!
5. that's what i couldn't figure out about the 2nd one. you have to have 3 known values in order to do ratio/proportion. so i just made one up in order to have some kind of answer.

so on the 2nd one, you say it depends on what the diluent is....what are the choices to dilute with? is that something like NS, LR, or D5W??
6. Hey Val, when all else fails I always read the vial. Every powder I've ever reconstituted will tell you how much dilutent to add, and the final concentration.

Sorry I can't be of more help, but nicoleinphilly tapped all of the brain energy I dedicated to math this week

Heather
7. :chuckle @ heather

unfortunately, when we are taking math exams in class, we don't have the vial in front of us to give us the answer.
8. I think the whole question is whacky! If I want to know how much diluent to add to make whatever, it should be ON THE VIAL, and if not, check the package insert (or at least that is what I was taught before)?!!

Darn instructors want us to pull a number out of thin air though. That is what fouls me up!

Anyway, I worked those problems (there were 50 and those were numbers 44 and 50 so my brain was probably fried) over and over so I think I *might* have figured out enough to get the grade. Since the 2nd was an IM medication, I would want to reconstitute with a small amount but geesh.... I sure hope they don't muck us up with ?'s like this on the exam.
Last edit by Vsummer1 on Oct 24, '02
9. OK, so I'm a lazy ass and didn't entirely read the question. :uhoh21:

The first one is 20mL's. But I didn't use a formula, just kinda looked at it. 1,000,000units per mL.....

Now the second one? Rena's right. You're missing a 3rd variable. You could make it up, but it would be more fun to call the teacher on leaving that info out. :chuckle

Great, now I'm tapped for 2 weeks!

Heather
10. Originally posted by Rena RN 2003
that's what i couldn't figure out about the 2nd one. you have to have 3 known values in order to do ratio/proportion. so i just made one up in order to have some kind of answer.

so on the 2nd one, you say it depends on what the diluent is....what are the choices to dilute with? is that something like NS, LR, or D5W??
NO, that was the ENTIRE problem. No other information given. I think "call the pharmacy" or, better yet, the teacher who wrote this nonsense (as you both suggested)
Last edit by Vsummer1 on Oct 24, '02
11. Hi,

Mefoxin is given IV not IM.

PREPARATION OF SOLUTION:
For Vials: One gram should be constituted with at least 10 mL, and 2 grams with 10 or 20 mL, of Sterile Water for Injection, Bacteriostatic Water for Injection, 0.9 percent Sodium Chloride Injection, or 5 percent Dextrose Injection. These primary solutions may be further diluted in 50 to 1000 mL of the diluents listed under the Vials and Bulk Packages portion of the COMPATIBILITY AND STABILITY section.

Diluents: 0.9 percent Sodium Chloride Injection, 5 percent or 10 percent Dextrose Injection , 5 percent Dextrose and 0.9 percent Sodium Chloride Injection , 5 percent Dextrose Injection with 0.2 percent or 0.45 percent saline solution , Lactated Ringer's Injection , 5 percent Dextrose in Lactated Ringer's Injection , 10 percent invert sugar in water , 10 percent invert sugar in saline solution , 5 percent Sodium Bicarbonate Injection , M/6 sodium lactate solution , Mannitol 5% and 10%

Hope this helps. You can find alot of info at www.rxlist.com
12. Originally posted by SoFlRNStudent
Hi,

Mefoxin is given IV not IM.
Hope this helps. You can find alot of info at www.rxlist.com
in the event that the instructor's give us an answerable question

I am going to bookmark this site. This question was located in the "resource manual" of the program I am in. It was under the "math practice test" section. It was stated that if we could answer all the questions in this section with an 80% we would be ready to take the medications examination. We will have no med ref's with us, just their piece of paper and a calculator (thank God they realize calculator's exist). However, the exam would be FAILED at 80% (most likely due to these outdated, mis-stated, questions) so here I am trying to get 80% on the practice....

Now, mind you, I had to PAY about \$10 for this photocopied "resource manual" full of wonderful things like this question. I have found numerous fallacies within this \$10 mandatory publication, this particular question being one. In some instances, they want us to answer with gr (grains) using roman numerals (their answer) and others used 1.5 rather than iss. So, what the (insert swear word here) do they want??!!

I spoke with the instructor today, and they are "re-working" to update it. Yeah, okay, but what about ME?? I take this book as GOSPEL about the program! They have meds in here that are so outdated it is ludicrous to learn them, and too numerous to list here.

At first I was lost, now I am merely PO'd at the distraction.

:chuckle Vent over... carry on... I know I will get through / over this but meanwhile, this is a PASS/FAIL test !!! Thus, the stupidity encountered on test ? no's 44 and 50, the ones I posted here. BRAIN IS FRIED!
13. Originally posted by SoFlRNStudent
Hi,

Hope this helps. You can find alot of info at www.rxlist.com
AND ON ANOTHER NOTE::::

WELCOME TO THE BOARD!! I noticed this was your 2nd post and I thank you for the great link and timely information!

Sorry I failed to mention that in my previous (venting) post... :imbar
14. Hey Val !
There's a GREAT little book that I'm SURE will be of help to you...best one I've found yet to explain SIMPLY and in a fun way all the tough stuff. Helped me a LOT. I'm a visual learner, and this book was perfect ! I'll pm you..don't think we're supposed to "advertise" here? You'll find it usesful even after school. Check it out and see what you think.