Nursing Students General Students
Published Aug 18, 2007
grannypatches, BSN, LPN, RN
31 Posts
Help! I have a drug dosage calculations test Wed. If I don't pass this test then I can't complete the last semester of the lpn program. I am a december candidate for graduation. The practice problems we were given to work on has confused me. THere are two questions that no matter what formula I use I don't get the right answer.
#1
Amoxicillin 50mg/kg po per day
Available: Amoxicillin 125g/2ml
Child weighs: 22 lbs.
Give:_______
#2
Order: Amoxicillin 75mg PO every 8 hrs.
Available: Amoxicillin 125mg/5ml
child weight: 70lb
pediatric dose parameter: 20-40 mg/lg in three divided doses
a) How many mg of Amoxicillin would the child receive per day?
b) Is the dose within safe parameters?
c) How many ml of Amoxicillin would the child receive per dose?
Answers given:
#1 8ml
#2 225mg/day
yes
3 ml
The formulas I am using are not giving me the correct answers. There is something I am doing wrong. Can someone plz help me? It would be deeply appreciated.
AnnieOaklyRN, BSN, RN, EMT-P
2,577 Posts
hi,
first you need to convert lbs to kg:
weight in pounds divided by 2.2 = kilogram weight.
multiply kg weight time dose per kilogram and that will give you your mg dose.
when you figure out the total daily mg dose divide that by the number of times per a day the child will receive a dose and that will give you the amount per dose.
* obviously when you find the mg dose you need to figure out how many mLs to give. Figure out how many mg are in 1 ml and then divide ordered dose by whatever is in 1 mL.
** Do not round until you get your final figure
Good luck
Sweetooth
traumaRUs, MSN, APRN
88 Articles; 21,250 Posts
I always use ratio and per cent because I have to keep things simple. So...for the first problem:
So, first I would get the child's weight from pounds to kilos:
22 pounds divided by 2.2 = 10 kg
Then, you know the dosage is 50mg per kg per day, so you multiply the 10 kg (child's weight) x 50mg = 500mg per day is the total dosage that the child receives per day. However, my next question is how often is this ordered: 3-4 times per day. The 500mg is what is to be given for the entire day, not in one dose! So..I would ask how often is this to be given???
However, just for the sake of figuring this problem: you have 125mg/2ml (or cc). You need to give 500mg, so you set it up as a ratio:
125mg 500mg
______ : : ______
2ml X
So, you multiply 500 x 2 = 1000
Then, you divide the 1000 by 125 = 8cc which is the dosage that you give.
That is what was puzzling me. It did not say how many times a day. It seemed to be in one dose and that seemed to me to be too much. Thanks for all the posts. It has got me started. Have a nice weekend everyone.
Daytonite, BSN, RN
1 Article; 14,604 Posts
i like to do these problems by dimensional analysis (factor label method) when they involve applying conversion factors. i still use the formula "dose desired divided by dose on hand" as a guide to what i am doing. however, i manipulate all the terms of the resulting problem to that i am going to end up with the correct label on the final answer.
#1 amoxicillin 50mg/kg po per dayavailable: amoxicillin 125mg/2mlchild weighs: 22 lbs.give:_______answer: 8 ml
amoxicillin 50mg/kg po per day
available: amoxicillin 125mg/2ml
child weighs: 22 lbs.
give:_______
answer: 8 ml
#2order: amoxicillin 75mg po every 8 hrs.available: amoxicillin 125mg/5mlchild weight: 70lbpediatric dose parameter: 20-40 mg/kg in three divided dosesa) how many mg of amoxicillin would the child receive per day?b) is the dose within safe parameters?c) how many ml of amoxicillin would the child receive per dose? answers: 225mg/day, yes, and 3 ml
order: amoxicillin 75mg po every 8 hrs.
available: amoxicillin 125mg/5ml
pediatric dose parameter: 20-40 mg/kg in three divided doses
a) how many mg of amoxicillin would the child receive per day?
b) is the dose within safe parameters?
c) how many ml of amoxicillin would the child receive per dose?
answers: 225mg/day, yes, and 3 ml
let me tackle "c" first:
hope that helps you and didn't confuse you. you might want to print this out and rewrite the fractions in a vertical position. i am not able to do that with this software.
Thank you so much for your help. I understood it completely. This is going to help me so much. I cannot thank you enough. Have a very nice weekend.