try to solve this!
Hello ,this is my first post,i am immigrating to Canada next summer and i am preparing for the PEBC ,i started with calculations (it wasn't good idea after all) ,well after 3 days of study(3 hours per day) i can say i have the basics now ,but this question below i don't know what they want so if anyone can help not by giving the final answer but how he understand it it will be great,by the way my e mail is
if any one wants to share some PEBC information
question: 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 1 g vial)
approximate concentration(mg/ml) volume
200 4.2
250 3.2
400 1.8
reconstituting at the lowest possible concentration,what volume in ml would be withdrawn to obtain one day's dose for a 50-lb child?
a- 3.4 ml b- 22.73ml c- 2.50 ml d- 2.27 ml
it is from CPR six edition chapter 2,so u 2 feel strange about it.
Adult dose is given : 30mg/kg.
Child weight : 50 lb.
1.first, we will calculate the dose needed for child.
A)
so 1000gm requires 30mg of drug,
then for 454gm (1 lb) _____ of dose requires.
Thus, 13.62 mg of dose is required for 1lb.
B)
1 lb requires 13.62 mg
so 50lb requires_____mg.
Thus, 50lb child requires 681mg.
2. But, I don't know next step? !!!!!!!!!!!!
But it states that 30mg/kg is the dose for children (which is about right)
Ok this is a very strange question but this could be how the PEBC asks you a calculation question. You are given a lot of information here that you just do not need, perhaps it is there to just to confuse, or perhaps it's to make it more like a real life situation. Remember calculation questions are not just about doing the math, they may also test your ability to interpret what is required and to extract the required information from the question.
So your first step is to figure out what they are asking for:
What volume of reconstituted drug would need to be drawn up to obtain one days dose for a 50lb child.
Simple enough. The hard part is getting the numbers you need to find this answer. So lets write out what you know and see if you need the information:
- Childs dose of Streptomycin 30mg/kg daily.....Required
- Given in divided doses every 6-12 hours.......Not Required
(they are asking for the dose for the whole day not an individual dose) - The dry powder is dissolved by adding water for injection USP in an amount to yield the desired concentration.......(for a 1g vial).........Not Required
(very interesting and all, but they are telling you which concentrations are available to you, you do not need to figure it out). - So now they are saying there are three concentrations of drug available, but they have told you to use the lowest possible concentration...therefore:
200mg/ml.............Required
250mg/ml.............Not Required
400mg/ml.............Not Required - Volume
4.2.............Not Required
3.2.............Not Required
1.8.............Not Required
(we do not need to know how they make the solution, just what concentration of solution we are using).
See, lots of useless information to try and throw you off.
So now we know what the concentration of the solution is we are going to use, we know what the weight of the child is (we just need to convert it to Kg) and we can figure out how much drug is required for the daily dose. Now using the above try and figure out how much of the solution you need to draw up.
I will post the full answer if requested.
Good luck,
Mat
The dose is 30mg/kg
so it is 681mg for 22.7kg
lowest conc has 200mg in 1 ml
so 681mg is in 3.4 ml
Correct
thanx very much matt,it is really the real life calculations,
l'optimisme de la volonte et la pessimisme de l'intelligence
Hi,
I thought for half an hour after finding child's dose. But, It was so simple.........!!!!!!!!!!!!
thanks
Hi Hussein,
Where did you get this question from originally. I would like to take a look at the original question if possible.
Thanks,
Mat