# dosage calculation

1. I am doing a dosage calculation problem and my instructor have not given me the answer sheet and I feel like I am not getting the right answer. I was someone can help correct my answer.

Question: The school nurse needs to administer ibuprofen 10mg/kg PO Q 4H. The client weighs 17lb. How many mg will the nurse administer per day.

How I set up my problem

10mg/kg x 17lb X 4hrs x 24hr/1 day x 1 kg/ 2.2lb

I got 4080/8.8 =463.6 mg/day

* I put 4hrs on the bottom
Last edit by Grnbay on Jan 12
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Joined: Dec '16; Posts: 10; Likes: 1

3. I did my calculation as (14lbs/2.2kh) *10mg/kg* 6 doses and got 382 mg rounded up
4. 17 pound school age child?????
5. You got the right answer but your problem set up looks wierd...i always convert lb to kg and then do the rest. Anyhow, i guess it doesnt matter as long as you get the answer.

As a side note, kindof a dumb question, since school nurses would not be working round the clock, so why 24 hours, and as someone above said, whats up with a 17lb child? but oh well...
6. I'm just going but what they are giving me
7. It's what my instructor had as a question and I am just going with it. Thanks
8. dimensional analysis is great, it is what I taught for a long time.

But you can do this a little more easily: convert lbs to kg answer 7.73 kg. 10mgs/kg gives you a dose of 77.3 mg.

Giving a dose every 4 hours is 6 doses in 24.

6 x 77.3 =463.8 mg in 24 hours.

So yes, you did it right.
9. "4hrs x 24hr/1 day" should be:

(24hrs/1day)/4hrs = 6
10. You have the correct answer - 463.6 mg/day

I usually always use dimensional analysis too. I like being able to follow along the path cancelling out what I don't need to get what I do need. But, the only thing you had to convert was lb to kg...you didn't have to go from like mg to mL, so as JBudd stated here you could have just converted the lb to kg, multiplied by 10 mg/kg, and got the mg/dose. Then, multiply by 6 because every 4 hours = 6x/day.

It seems weird to me to do it x 4 hrs and then use 24 hrs/1 day. I have never done it that way! I always change it to doses. So if the order is for every 4 hrs, I will change it to 6 doses/day. So I would set it up like this:

11. The answer should be to give 80 mg/4ml (because I know it comes 100 mg/5 ml) q6. It's not a q4 med. The calculation comes out to 77 mg, but we give 80. I actually know some PAs who write take home pharmacy orders for things like 77 mg of ibu and then the poor parents can't figure out what to do. Honestly, I'm worried about your instructor. The 17 pound child, the q 4 ibu. She may need an intervention. Get the epocrates app right now!! The free version will change your life. I use it at work/clinicals. Life changer.
12. Quote from LucyLou88
The answer should be to give 80 mg/4ml (because I know it comes 100 mg/5 ml) q6. It's not a q4 med. The calculation comes out to 77 mg, but we give 80. I actually know some PAs who write take home pharmacy orders for things like 77 mg of ibu and then the poor parents can't figure out what to do. Honestly, I'm worried about your instructor. The 17 pound child, the q 4 ibu. She may need an intervention. Get the epocrates app right now!! The free version will change your life. I use it at work/clinicals. Life changer.
The problem (with goofy weight and everything) does not provide the "on hand" concentration of the Ibuprofen, so no, the answer is NOT 80mg/4ml.
13. Quote from Mavrick
The problem (with goofy weight and everything) does not provide the "on hand" concentration of the Ibuprofen, so no, the answer is NOT 80mg/4ml.
Liquid ibuprofen only comes in 100mg/ 5ml.
14. Quote from JBudd
Liquid ibuprofen only comes in 100mg/ 5ml.
In the real world, yes; however, there was very little real world in the problem the OP posted. And, based upon some of the problems posted here this is becoming more common. Whether they are trying to make the problem more "challenging" or just don't know the medication and don't care enough to look it up isn't clear.

Either way, I think it sad, and think it sends a bad message to the students.