Calculation

[nimji]

Hi

 

I am a new member of this forum. I am also going to be appear in june 2008 exam. I am not able to solve the following question from CPR 6th edition. Chapter2 study questionn 11. Can anybody help me to solve this problem

 

eg.The recommended maintenance dose of aminophylline for children is 1.0/mg/kg/hr by injection. If 10 ml of 25 mg/ml solution of aminophylline is added to a 100 ml bottle for dextrose, what should be the rate of delivery in ml/hr for a 40lb child?

 

(a) 2.30 ml/hr

(b) 8.0 ml/hr

© 18.9 ml/hr

(d) 18.2 ml/hr

[pinky786]

Hi Nimji!

 

Here the answer,

 

Convert body weight to kg, its going to be 18.18kg.

Dose is 1mg/kg/hr, so 1 x 18.18 = 18.18 kg/hr

We are adding 25 mg/ml of 10ml to 100 ml of dextrose 25 x 10= 250mg/10 ml+100ml dextrose,

So 250 mg is now present in 110ml, divide 250/110=2.27mg/ml

Now divide 18.18/2.27=8 ml/hr,

 

I hope this will help,

 

Goodluck,

 

pinky786

[nimji]

thank you very much pinky786.

[nimji]

Hi

I have two more questions regarding calculations.

 

1) For Children streptomycin is to be administered at a dose of 30 mg/kg of body weight daily in divided doses every 6-12 hr. The dry powder is dissolved by adding water for injection USP in an amount to yield the desired concentration as indicated in the following table ( for a 1g vial)

 

Approximate conc. (mg/ml) volume(ml)

200 4.2

250 3.2

400 1.8

 

Reconstituting at the lowest possible conc.what volume (in ml) would be withdrawn to obtian one day's dose for a 50lb child?

 

(a) 3.4 ml

(b) 22.73 ml

© 2.50 ml

(d) 2.27 ml

 

 

2) How many grams of talc should be added to 1lb of a powder containing 20 gm of zinc undecylenate per 100 gm to reduce the concentration of zinc undecyclenate to 3%

 

(a) 3026.7g

(b) 2572.7 g

© 17 g

(d) 257 g

[pinky786]

Hi Nimji!

Q.NO.1

Child weight in kg = 22.7kg

Dose is 30mg/kg x 22.7= 681.82 mg

Take the lowest possible concentration

200 mg is in 1ml

681 mg in x ml

 

x=681/200=3.4ml

 

I will post the 2 nd later.

 

pinky786

[nimji]

Thank you very much.

[nimji]

Hi can any body give me the solution for my second question? Thank you very much in advance

[lorliw]

For the 2nd calculation:

20 gram in 100 gram = 3 grams in X

20 x 100 divided by 3 = 666 gram

666 x 4.54 ( b/c 1 lb=454 gram) = 3026 gram total weight

3026- 454 (b/c you are adding the talc to 1lb of drug)= 2572 gram of talc added to 1 lb of drug

 

To double check:

1 lb of 20 gram in 100 gram (20%), you would have a total of 90.8 gram of drug.

If you want a final conc of 3 g in 100 gram, then 90.8 gram would be in a total of 3026 gram. (Again 3026-454=2572)

[nimji]

Hi lorliw,

 

Thank you very much for your help.