dosage calculations

[santuono]

I was hoping someone could help me out with some math questions...I really have trouble figuring out the problems involving reconstitution. If anyone could just help me with how to set up the problem and the steps to figure it out, I would really appreciate it!! I am not just looking for answers but actually how to go about setting up the formula and figuring it out...Thanks!

Some examples...

Prescribed is erythromycin 250mg of oral suspension. The label on the vial of erythromycin 0.4 gram states to reconsitute granules with water to achieve a concentration of 100mg/5mL. The nurse should administer how many mL to achieve the prescribed dose?

Prescribed is ertapenem 300 mg IV every 12 hours for 10 days. The label on the vial of 1 gram of ertapenem reads to reconsitute to achieve a concentration of 20mg/mL. The nurse should administer how many mL of reconstitued medication to achieve the presecribed dose?

Prescribed is amphetamine sulfate 20mg three times a day for ADD. The pharmacy supplies 10 mg tablets. The client is unable to swallow tablets, so the nurse crushes each tablet in 2 mL of water and a drop of cherry syrup. The nurse should adminster how many mL for each dose?

[kimmie4476, ASN, RN]

Maybe you are just over thinking these as is the case a lot of times with reconstitution problems. There are a lot of extra words there you don't need.

For example number 1, the dose needed is 250mg

the dose on hand is 100mg per 5 ml

and that is all you need to know to answer the question. Answer is 2.5ml

Example 2 All you need is the dose needed 300mg

dose on hand 20mg/ml

hope this helps some!

[BacktotheBeach, ADN, BSN, RN]

this website is wonderful for all kinds of practice problems and explanations. http://www.dosagehelp.com/

[ParkerBC,MSN,RN, PhD, RN]

Maybe you are just over thinking these as is the case a lot of times with reconstitution problems. There are a lot of extra words there you don't need.

For example number 1, the dose needed is 250mg

the dose on hand is 100mg per 5 ml

and that is all you need to know to answer the question. Answer is 2.5ml

Example 2 All you need is the dose needed 300mg

dose on hand 20mg/ml

hope this helps some!

Question # 1:

If you give 2.5ml, you are only administering 50mg, not 250mg.

250/100 X 5ml = 12.5mL This is the correct dosage amount.

Question # 2:

300mg/20mg X 1ml = 15ml

Question # 3:

Since the medication you are mentioning is a stimulant, it should not be crushed. If that part doesn't matter to your instructor and she/he asks what you would administer if it was a drug that could be crushed, the number of mL doesn't matter so as long as you crushed two tabs for each medication administration.

[kimmie4476, ASN, RN]

my bad on the first one, it's been a long night shift! This is why when you are working and tired, you always have someone double check your calculations! but the object was to show how you get rid of all the extra words around the problem that you don't need.

[ParkerBC,MSN,RN, PhD, RN]

It’s okay. It was good advice. I just hoped it wasn’t the OP’s original homework question. Anyway, have you always worked nights? How did you get yourself prepared to work the night shift? I will be offered a night position, but have never worked nights. Suggestions?