HELP SOME MORE

I am a CNA trying for my pharmacy tech certificate I am also a medicene tech.
I have tried everything, I have a problem with rounding off numbers.
Here are the questions:
1)Calculate the number of mL to administer with each dose. Round your answer to the nearest tenth.
Ordered: Chloroquine hydrochloride 300 mg IM daily
On hand: Chloroquine hydrocholride 200 mg/mL 5mL MultiDose Vial
I came up with 7.5, but I think it is wrong.
2)Calculate the number of mL to administer with each dose. Round your answer to the nearest tenth.
Ordered: Epoetin Alfa 2500 units subq tiw
On hand: Epoetin Alfa 4000 units/mL SingleDose Vial
I came up with 1.5ml 
May 28, '091)Calculate the number of mL to administer with each dose. Round your answer to the nearest tenth.
Ordered: Chloroquine hydrochloride 300 mg IM daily
On hand: Chloroquine hydrocholride 200 mg/mL 5mL MultiDose Vial
I came up with 7.5, but I think it is wrong.
200mg:5cc::300mg:x cc
200x=300 X 5
200x= 1500
x = 1500 divided by 200 (1500/200)
x = 7.5cc (you're right!!)
2)Calculate the number of mL to administer with each dose. Round your answer to the nearest tenth.
Ordered: Epoetin Alfa 2500 units subq tiw
On hand: Epoetin Alfa 4000 units/mL SingleDose Vial
I came up with 1.5ml
4000units : 1 cc :: 2500units : ?cc (also known as x)
4000x = 2500
x = 4000/2500
x=1.6cc No need to round, the .6 IS in the tenths spot
Here's info about rounding: http://www.321know.com/g44c_wx1.htm It's a kids site, but I used it this school year to help my son figure it out when he just could not get it from the book or from me!
"Rounding decimals is very similar to rounding other numbers. If the hundredths and thousandths places of a decimal is fortynine or less, they are dropped and the tenths place does not change.
For example, rounding 0.843 to the nearest tenth would give 0.8.
If the hundredths and thousandths places are fifty or more, the tenths place is increased by one. The decimal 0.866 rounded to the nearest tenth is 0.9"
</B> 

May 28, '09A little common sense and BASIC math will go a long way. The more steps you put into an equation, the more places there are for you to make a mistake.
What you have on hand is 4000mg/ml.
What you need to give is 2500mg.
Right off the bat you know that the answer HAS to be less than 1 ml, because you will be giving way less than 4000mg. That's where logic helps you save the day.
What's the simplest way?
Convert to fractions.
2500

4000
Now reduce it to its simplest terms. Eliminate the zeroes. That leaves:
25

40 of a ml
Is there a common denominator? Yes! They are both divisible by 5. That will bring it down to single digits.
5

8
You now know that 2500mg is 5/8 of 4000mg, and logically speaking that seems about right, don't you think? If you already know in your head that 1/8 is equal to 12.5% then you would multiply by 5 to get 62.5% or .625.
If you don't already know that in your head, just use your trusty calculator to divide 5 by 8 to find out what 5/8 equals.
Since this is a question about rounding off, my answer would be .63ml.
Please try to simplify your problems as much as possible and double check them with logic. This will take away a lot of the fear of math. If you wish to eliminate all of the reduction from 2500/4000 to 5/8 and have a calculator, just remember to always divide the amount you have available into the amount you want. When you are dealing with medicines that are listed per 5ml or 10ml or whateverfirst divide by that number to find out how many mg per 1ml and then divide that amount into the amount you want to give. It is so much easier.
Good luck to you! 
May 28, '09Quote from mnono009No, that isn't correct although the first time I did it I got fooled too. The dose concentration is 200mg/ml. The 5ml part is known as a "distractor" . It has nothing to do with the equation. Also, if you notice this is an IM medication. We rarely give IM's with that volume. It would take at least three injections. So the calculation would be the standard:1)Calculate the number of mL to administer with each dose. Round your answer to the nearest tenth.
Ordered: Chloroquine hydrochloride 300 mg IM daily
On hand: Chloroquine hydrocholride 200 mg/mL 5mL MultiDose Vial
I came up with 7.5, but I think it is wrong.
200mg:5cc::300mg:x cc
200x=300 X 5
200x= 1500
x = 1500 divided by 200 (1500/200)
x = 7.5cc (you're right!!)
</B>
200mg:1ml, 300mg:x ml200x=300x=300 divided by 200x=1.5
Last edit by FlyingScot on May 28, '09 
May 28, '09Quote from FlyingScotWrong! The 5ml part is very important! 200 mg in 5 ml is a very different concentration than 200mg/ml. If your concentration is 200 mg in 5 ml, and you need to give 300 mg, then you will need to give more than 5 mlcommon sense.No, that isn't correct although the first time I did it I got fooled too. The dose concentration is 200mg/ml. The 5ml part is known as a "distractor" . It has nothing to do with the equation. Also, if you notice this is an IM medication. We rarely give IM's with that volume. It would take at least three injections. So the calculation would be the standard:
200mg:1ml, 300mg:x ml200x=300x=300 divided by 200x=1.5
Using basic dimensional analysis, what is ordered divided by what is on hand:
300(mg) 5ml 1500 15
 x  =  > simplify  > simplify 7.5ml
1 200(mg) 200 2 
May 28, '09You didn't look at the problem. It clearly states "200mg/ml in a 5ml multi use vial" So that means in that vial is a total of 1000mg with each ml containing 200mg. In addition the volume of 7.5ml is inappropriate for an IM injection.

May 28, '09Quote from justt139Always start with what is ordered, then divide by what is on hand:2)Calculate the number of mL to administer with each dose. Round your answer to the nearest tenth.
Ordered: Epoetin Alfa 2500 units subq tiw
On hand: Epoetin Alfa 4000 units/mL SingleDose Vial
I came up with 1.5ml
2500 units 1ml
 x  
1 4000 units
or more simply, 2500 units divided by 4000 units (since what you have on hand is 4000 units per ml)
answer is 0.625 ml, rounded to the nearest tenth is 0.6 ml. 
May 28, '09Quote from FlyingScotAha! You're right! Mea culpa!You didn't look at the problem. It clearly states "200mg/ml in a 5ml multi use vial" So that means in that vial is a total of 1000mg with each ml containing 200mg. In addition the volume of 7.5ml is inappropriate for an IM injection.

May 28, '09No problem. At least the OP shouldn't feel too badly about getting it since it fooled some seasoned nurses as well.

May 28, '09My goodness, do we get calculators in the med room or we have to do all of this off the top of our heads?! Haha


May 29, '09Quote from annod81yes..this must be memorized.My goodness, do we get calculators in the med room or we have to do all of this off the top of our heads?! Haha