Help with a dosage calculation

[dannyb83]

A nurse is preparing administer ampicillin 25 mg/kg PO divided in equal doses every 12 hrs to an adolescent who weighs 99 lbs.The amount available is ampicillin suspension 50mg/5ml.How many ml should the nurse administer per dose

[loriangel14, RN]

Have you tried to figure this out on your own? You won't learn if we do it for you. First you need to convert the weight to kilograms. Do that and then let's us know what each dose will be.

[dannyb83]

Yes and I got 5ml.....but it's wrong and I can't figure out why

[dannyb83]

Ok so now this is the steps to took but insure if it's right...99÷2.2=45 45×25=1125 1125÷50=22.5 22.5×5=112.5ml....but I don't know if that's rigjt or if I did it correct

[Lesia321, ADN, BSN, RN, EMT-B]

I totally missed the divided dose part.

[loriangel14, RN]

You divide the 1125 in half not by 50.

[loriangel14, RN]

562.5

[klone, MSN, RN]

562.5

That's the total mgs, not total ml

[klone, MSN, RN]

Ok so now this is the steps to took but insure if it's right...99÷2.2=45 45×25=1125 1125÷50=22.5 22.5×5=112.5ml....but I don't know if that's rigjt or if I did it correct

You were correct through the bolded. I assume the 25mg/kg PO is the daily dose. If so, then it needs to be divided by 2, not by 50 (since 1125 is daily dose, and it's being given BID).

[loriangel14, RN]

That's the total mgs, not total ml

I know. I was working it through step by step.

[loriangel14, RN]

50 mg per 5 ml works out to 10 per ml. 562.5 Mgs would be 56.25 mls

[TheCommuter, BSN, RN]

Moved to the Nursing Student Assistance forum.