[flames9]

Originally Posted by beth66335

Here it is in DA:

100ml X 60min = 6000 = 200ml/hr
30min.... 1hr...... 30

You do have 1 g in the bag according to the problem not 900mg, does this make more sense? I have trouble with this too, I can see the answer before i work the problem then I have a hard time figuring out how to set it up so the teacher understands my thinking!

Yes I relaize the bag does have 1 gram, the 900mg I stated was just an example

thanks

[beth66335]

Oh I see...sorry!

[shrimpchips]

Help!

I don't have to take an NET exam...instead I have to take this ProCalc math test before I can start clinicals. We went over dosage calculations over one 4-hour period the FIRST week of class and that was it. Our instructors told us to read the first 11 chapters of our books (which was basic math like decimals, fractions, percentages, etc). we spent a long time on that stuff but when it came to the dosage calculations, they FLEW through them! They kept putting the easy problems on the board and simply "read off" the harder ones.

I have to get a 90% or better on this test and I have 3 tries to do it. Right now I am at 77% proficiency and it's all because of problems like these:

1,000 mg of Ceptaz (ceftazidime) must be prepared. A 1 grams vial of Ceptaz in powdered form is available. Directions for reconstitution state: Add 10 mL of diluent to yield 90 mg in 1 mL. After reconstituting the drug as directed, how many mL should you withdraw from the vial?

... I don't even know where to START with that one. I'm getting really nervous about this test

Then there was another one that I got wrong:

You need to verify that a prescribed dose of Apresoline (hydralazine hydrochloride) for a patient currently weighing 86 lbs is safe. The drug literature recommends a maximum of 7.5 mg/kg/day. The drug is administered in 2 divided doses over a 24-hour period. You determine that a maximum safe dose for this patient would be __ mg per dose.

Here is what I did:

86 lbs / 2.2 kg = 39 kg

39 kg x 7.5 mg = 292.5 mg

292.5 mg / 2 = 146.25 = 146.3 mg/dose

...yet the correct answer is 147 mg/dose and I don't understand why?


...I hate nursing math.

[Daytonite]

1,000 mg of Ceptaz (ceftazidime) must be prepared. A 1 grams vial of Ceptaz in powdered form is available. Directions for reconstitution state: Add 10 mL of diluent to yield 90 mg in 1 mL. After reconstituting the drug as directed, how many mL should you withdraw from the vial?

90mg/1mL (concentration in vial after constitution) = 1 gram/X mL (since the vial says it contains 1 gram)
Covert grams to milligrams first. 1 gram = 1000 mg.
So, 90mg/1mL = 1000 mg/X mL
Cross multiply and solve for X.
90X = 1000, X = 11.1111, round off, so X = 11.
You would draw 11 mL from the vial.

You need to verify that a prescribed dose of Apresoline (hydralazine hydrochloride) for a patient currently weighing 86 lbs is safe. The drug literature recommends a maximum of 7.5 mg/kg/day. The drug is administered in 2 divided doses over a 24-hour period. You determine that a maximum safe dose for this patient would be __ mg per dose.

Here is what I did:

86 lbs / 2.2 kg = 39 kg

39 kg x 7.5 mg = 292.5 mg

292.5 mg / 2 = 146.25 = 146.3 mg/dose

...yet the correct answer is 147 mg/dose and I don't understand why?

When I do this by dimensional analysis instead of breaking it down into individual calculations I come up with the lost digit:

7.5 mg/kg (dose desired) x 86 lbs/day x 1 kg/2.2 lbs (conversion factor) x 1 day/2 doses in a day = 146.59 mg/dose, rounds off to 147 mg/dose

[shrimpchips]

thank you, Daytonite!!!

the first one really confused me with the whole "add 10 mL of diluent to yield 90 mg in 1 mL." But it makes sense and actually that problem was a lot easier than I thought after seeing what you did to come up with the answer

as for the second one, I really hope that test isn't going to make me solve by dimensional analysis just to get the CORRECT answer because dimensional analysis confuses me. i prefer solving by proportion/ratio or the D/H x Q formula.

thank you again!!! this really helps!

[2bNewRN2010]

I'm working on basic drug calculations and I'm having trouble with 2 questions. This isn't homework, just a practice problem.

The adult dose of a medication is 50 mg.
The dose for a child whose BSA is 0.70 m2 is _____ mg.

correct answer 20.23 (I have no idea how they got that)

Child's BSA: 1.1 m2
Order: Betamethasone 4 mg/m2/day PO, divided into four doses is ordered.
Available: syrup 0.6 mg/5 mL
How many mL will you administer per dose?

correct answer 3.66

Any help is greatly appreciated!!

[Sunkissd01]

Thankyou!!!!!

[Daytonite]

Originally Posted by 2bNewRN2010

I'm working on basic drug calculations and I'm having trouble with 2 questions. This isn't homework, just a practice problem.

The adult dose of a medication is 50 mg.
The dose for a child whose BSA is 0.70 m2 is _____ mg.

correct answer 20.23 (I have no idea how they got that)

Child's BSA: 1.1 m2
Order: Betamethasone 4 mg/m2/day PO, divided into four doses is ordered.
Available: syrup 0.6 mg/5 mL
How many mL will you administer per dose?

correct answer 3.66

Any help is greatly appreciated!!

The adult dose of a medication is 50 mg.
The dose for a child whose BSA is 0.70 m2 is _____ mg.

correct answer 20.23 (I have no idea how they got that)

If you have a textbook there should be information in it or the index on how to convert the BSA to the patient's weight or a formula you need to be using such as this one listed in
http://www.lww.com/promos1/karch/images/05-Karch.pdf which states "The formula for estimating a child’s dose is: Child’s BSA (in m2) adult dose x 1.73." That obviously isn't the formula they used for this problem, so there is some other factor they are using when converting the dosage. It is either somewhere in your textbook or will be given to you in a lecture. There are links to nornograms on post #3 of this thread.

Child's BSA: 1.1 m2
Order: Betamethasone 4 mg/m2/day PO, divided into four doses is ordered.
Available: syrup 0.6 mg/5 mL
How many mL will you administer per dose?

correct answer 3.66

I've worked this backward and forward and drawn a picture. I think your answer key is wrong.

Dose Desired: 4 mg/m2/day in four doses
Dose on Hand: 0.6 mg/5 mL
Given Information: child's BSA is 1.1 m2

4mg/1 m2 (dose desired) x 5 mL/0.6 mg ( dose on hand) x 1.1 m2 (child's BSA)/24 hours x 24 hours/4 doses (conversion of hours to # of doses in a 24-hour day) = 9.166, rounds to 9.2 mL/dose

[2bNewRN2010]

Thanks!! I thought the answer key was wrong because that answer just didn't make sense. I and thank you for the first answer too. I figured out what they did. The divided the child's BSA by 1.73
(mean average adult BSA) then multiplied it by the adult dosage.

[nurse4343]

The only thing that I can suggest is, go to a college library, get a good drug calculations book with lots of practice questions and practice, practice, practice...