oh my gosh, Can someone please help me with this drug calc problem??

I have probably spent 3+ on this one problem. Cannot figure it out at all.
The order is for Amoxicillin 20 mg/kg/day. This is to be divided into doses to be given every 6 hours to a child weighing 11 lbs. If the medicine is supplied as a solution of 500 mg/2mL, how much would you give for each dose?
I know you are supposed to put the child's weight in kg and I got 5 kg for that. and I'm lost after that
someone please help, im goin crazy! 

May 28, '0920mg / Kg/day * 11lbs/1 * 1Kg / 2.2lbs * 2ml / 500mg = 0.4 ml/day
> 0.4 ml / 4 = 0.1 ml /dose 
May 28, '09how do you know how to set up those boxes? i think they are called "idiot boxes"? i dont get it
why did you divide .4 by 4 at the end?
you are right though, the answer is 0.1 mL 

May 28, '09First:
11 lbs /2.2 = 5 kg
then
20mg/kg/day = 20mg * 5 kg = 100 mg/day
then
500mg/2ml = 100mg/x
cross multiply you get 200 = 500x = 0.4 ml total dose/day
then since the dose is to be divided into 4 doses (every 6 hours)
0.4ml/4 = 0.1 ml per 6 hour dose
I think that's right. 
May 28, '09bowingpur:heartbeat
you guys are so awesome. i love this forum, so helpful!!
MANY THANKS!!!! 
May 28, '09Quote from JadenRN TO BESolaireSolstice answered your questions.how do you know how to set up those boxes? i think they are called "idiot boxes"? i dont get it
why did you divide .4 by 4 at the end?
you are right though, the answer is 0.1 mL

May 28, '09Quote from PrincessSpyderI did the calculation only, I did not explain it though....Ice Cream...You're an awesome person for helping this person with the answer.

May 28, '09Jaden, try visualizing the problem and see if that helps you understand the steps.
Imagine actually having that patient and that medication to give. 
May 28, '09Hi there,
Now I"m don't do pediatrics, so I'm unfamiliar with their dosing, but based on your numbers, here's what I'm getting.
20 mg/kg/day as you point out this pt weighs 5 kg... Therefore the patient needs
20mg x 5 daily (100mg) in 4 equal doses = ammox 25mg every 6 hours
So your desired dose is 25 mg, what is your dose on hand?
500mg in 2cc = 250mg in 1cc ... Your dose on hand is 250mg/1cc
divide your desired dose by your dose on hand 25 divided by 250 = 0.1cc
Your patient needs 0.1cc of this ammox every 6 hours. Certainly a smaller dose than I am used too!
Hope this helps
From the white mountains of NH 
May 28, '09The order is for Amoxicillin 20 mg/kg/day. This is to be divided into doses to be given every 6 hours to a child weighing 11 lbs. If the medicine is supplied as a solution of 500 mg/2mL, how much would you give for each dose?
Dose Desired: 20 mg/kg/day q6h (q6h means there will be 4 doses given over a 24 hour day)
Dose on Hand: 500 mg/2 mL
Child's Weight: 11 pounds
Conversion Factor: 2.2 pounds = 1 kg
By dimensional analysis (factor labeling): 20 mg (dose desired)/500 mg (dose on hand) x 11 pounds (weight of child)/1 kg (part of dose desired) x 1 kg/2.2 pound (conversion factor) x 2 mL (amount the dose in hand comes in)/4 (number of doses this needs to be divided into) = 0.1 mL (amount to give for one dose)