Dosing Calculation help


so this is the problem I can't figure out. I think the answer is: No, it is unsafe dose because 60 mg q.8h would be a total of 180 mg, and using the 15 mg/kg/day formula the max for this kid would be 109 mg.... but what is this 1.5g/day max? is that the max dose for the drug?

Order: Kantrex 60 mg IV q. 8h for a child who weighs 16 lbs.

The recommended dose for adults and children is 15 mg/kg/day in 2-3 divided doses, not to exceed 1.5 g/day.

Supply: Kantrex 75 mg/2 mL.

Is this dose safe? If so how much do you administer?

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Rose_Queen, BSN, MSN, RN

6 Articles; 11,338 Posts

Specializes in OR, Nursing Professional Development. Has 18 years experience.

Your math is correct in that the prescribed dose is 180 while the max recommended would be 109. The max dose per day simply means that should you have a rather large patient, you should not exceed 1.5 grams even if their weight calculates a higher dose.


2 Posts

thank you! That is what I thought but math isn't my best subject so I was doubting myself.

bgxyrnf, MSN, RN

1,208 Posts

Specializes in Med-Tele; ED; ICU. Has 10 years experience.

General advice:

Learn not to doubt yourself unless there's a reason to question your results.

Continue to develop a sense of rationality applied to your answers (i.e. "does this make sense?")

Don't just review problems that you got wrong, review ones that you got right in order to see why they were right and to reinforce correct problem-solving approaches.

Don't skip steps.

Be meticulous in carrying all of your units through each line of calculation... this is, IMO, the biggest problem that people have.

Before you set pencil to paper, or fingers to keyboard, try to think through what they're looking for and how you get there.

Steep yourself in the basic concepts such as mass, volume, concentration, quantity, ratios, and units of measure.

KelRN215, BSN, RN

1 Article; 7,349 Posts

Specializes in Pedi. Has 16 years experience.

The answer to the question as written on your exam would be no, the dose is unsafe as it exceeds 15 mg/kg/day.

HOWEVER, in practice there may well be a reason why this higher dose is being used and this should be discussed with Pharmacy and the Medical Team. I don't think I've ever seen a child with refractory seizures NOT on a dose of some antiepileptic that well exceeds the general recommended dose.