Omg, Help With Math Please

Super_RN, BSN, RN · Aug 25, 2005

hi all! im having the worst trouble with a math dosage assignment thats due before i go back to school. if anyone could possibly help (i dont even know where to begin or how to set up). im am so frusterated looking for a solution!
1) order: ampicillin 150mg im
label and instructions: ampicillin 500mg multidose vial. add 1.8ml diluent to yield a concentration of 250mg/ml.
how many ml's should the nurse administer?
150 / 250 =0.6ml
2) order:atropine sulfate grain 1/150 im
vial is labeled: atropine sulfate 0.4mg/ml
how many ml's should the nurse administer?
3) order: kcl 30 meq in 1000ml of d5.9 nss iv over 6 hours
label: potassium chloride (kcl) infection 40 meq in 30 ml
how many ml's of kcl should be added to the iv bag of d5.9 nss to provide the ordered dose of kcl 30 meq?
we never add kcl. pharmacy does
4) order: zantac 50mg iv q 8 hrs
ivpb bag is labeled: zantac 50mg in 50cc d5w to run over 30 minutes
the iv infusion pump should be set at what rate?
50 ml x 60 min=3000 3000 / 30 min= 100 ml/hr
5) order: heparin 800 units.hour iv
the premixed iv bag is labeled: heparin 25,000 units in 250cc 5% dw
the iv infusion pump shoould be set at what rate?
heparin infusions will run at double the first / second number. this one will run at 16, (800).
thanks for all of your help in advance.

i guess the main thing is getting these equations down. my answers aren't guaranteed right, but you definitely need to figure out how to do them. i am assuming they will teach you this in school and not just expect you to know it. good luck!

:nurse: jaime

canuckeh! · Aug 25, 2005

Hi All! Im having the worst trouble with a math dosage assignment thats due before I go back to school. If anyone could possibly help (I DONT EVEN KNOW WHERE TO BEGIN OR HOW TO SET UP). Im am so frusterated looking for a solution!
1) Order: Ampicillin 150mg IM
Label and instructions: Ampicillin 500mg multidose vial. Add 1.8ml diluent to yield a concentration of 250mg/ml.
How many ml's should the nurse administer?
Med dose calculations are based on ratios
If 1 ml of the solution after it is reconstituted gives you 250 mg, you want to know how many mls(x mls) you need to give 150 mg
1ml is to 250 as ?ml is to 150
1/250 =x/150
Multiply the top number on left side of the equal sign by the bottom number on the right side of the equal sign(150). Multiply the bottom number on the left side of the equal sign by the top number on the right side of the equal sign(250x)
Result 250x=150
divide 150 by 250
Give .6ml
2)Order:Atropine Sulfate grain 1/150 IM
Vial is labeled: Atropine sulfate 0.4mg/ml
How many ml's should the nurse administer?
First you need to know how many mg in a grain as you med is provided in mg.
A grain has 60 mg so the order for 1/150 grain is 60 divided by 150 equals .4 mg
Your solution has .4 mg in 1 ml so you give 1 ml.
Same math as above only this one is easy
3) Order: KCL 30 mEq in 1000ml of D5.9 NSS IV over 6 hours
Label: Potassium Chloride (KCL) infection 40 mEq in 30 ml
How many ml's of KCL should be added to the IV bag of D5.9 NSS to provide the ordered dose of KCL 30 mEq?
40 mEq/ 30 ml=30 mEq/x ml
Multiply the top number on left side of the equal sign by the bottom number on the right side of the equal sign(40x). Multiply the bottom number on the left side of the equal sign by the top number on the right side of the equal sign(900)
Result 40x=900
Divide 900 by 40
22.5 mls
4) Order: Zantac 50mg IV q 8 hrs
IVPB bag is labeled: Zantac 50mg in 50cc D5W to run over 30 minutes
The IV infusion pump should be set at what rate?
50 cc/30 min=xcc/60 min
Multiply the top number on left side of the equal sign by the bottom number on the right side of the equal sign(3000). Multiply the bottom number on the left sid eof the equal sign by the top number on the right side of the equal sign(30x)
30x=3000
x=100 cc's per hour
5) Order: Heparin 800 units.hour IV
The premixed IV bag is labeled: Heparin 25,000 units in 250cc 5% DW
The IV infusion pump shoould be set at what rate?
250 cc/25,00 units=x cc's/800 units
Multiply the top number on left side of the equal sign by the bottom number on the right side of the equal sign(200,000). Multiply the bottom number on the left side of the equal sign by the top number on the right side of the equal sign(2500x)
2500x=200,000
x=8 cc's per hour
Look up Pharmaceutical calculations in google and find a good practice site.
The key is understanding that you need to find a similar ratio to what you already know.
Thanks for all of your help in advance.

I'm great in math- not so great with computers. Sorry I didn't change the color of my answers. Hope it helps

truern · Aug 25, 2005

1) Ok, in this question they're trying to throw you off track by giving variables that you don't need, so concentrate on the things you *do* need to know..

Once you've reconstituted the medication, it yields: 250/mg/ml. Your order is for 150 mg..

250 mg/1 mL equals 150 mg/x mL.....cross multiply so 250 mg X x mL is 250x, and 150 mg X 1 mL is 150. 250x equals 150/250, which is 0.6. Since you were solving for mL, x equals 0.6 mL.

2) You know there are 60 mgs per 1 grain, so set up your problem as 60 mg/gr 1 equals x mg/gr 1/150. Cross multiply to get x = 60/150, which is 0.4 mg. The atropine comes 0.4 mg/mL, so 0.4 mg/1 mL : 0.4 mg/x mL...cross multiply to get x= 0.4/0.4, which is 1. Again, look to see what you solving for, which was mL, so it's 1 ml.

3) This is another one with extra numbers you need to ignore: the 1000 mL of IV solution. The potassium is labeled 40 mEq per 30 mL and your order is for 30 mEq, so you need to find out how many mLs you need to add to the IV. 40 mEq/30 mL : 30 mEq/x mL..Cross multiply for 40x = 900. Divide x by 40 to get the x by itself, then also divide the 900 by 40 (remember whatever you do to one side, you do to the other) x=22.5 mL In this case, you won't round up because you can draw up .5 mL.

4) If you're going to run 50 mg in 30 minutes, you would run x mg in 60 minutes, so 50 mg/30 minutes : x mg/60 minutes. Cross multiply to get 30x=3000/30 and x=100. You would set the IV pump to infuse at 100 mL/hour (not sure if you've had IV experience, but pumps are set at mL/hr)

5) 25,000 units/250 mL : 800 units/x mL equals 25,000 = 200,000. Divide both sides by the 25,000 to get x=8 mL/hr

You'll notice I never take "shortcuts" to arrive at my answer. I *always* do all the math and label each part of the equation just so I don't lose sight of what I'm solving for.

If it's any consolation, we were emailed a math packet at the beginning of summer and had our Med and IV calc test BEFORE our IV theory and lab. Some schools do indeed expect you to learn the math on your own, but it's doable. I made 100 on my exam

JKostok · Aug 25, 2005

You all are the best! Thank you for not only helping me but teaching me how. I had med dosage a year ago but for some reason they were never this hard! Guess I better practice practice practice! Thank you all so much! :)

Super_RN, BSN, RN · Aug 25, 2005

I'm great in math- not so great with computers. Sorry I didn't change the color of my answers. Hope it helps

Much better explanations than me! Great job!