Monday, March 21, 2011

The "Rule of 20" for Pediatric Amoxicillin Dosing

The Rule of 6 for dosing amoxicillin, which we discussed in a previous post, is probably outdated since amoxicillin is typically dosed 80 to 90 mg/kg/day instead of 40 mg/kg/day for children (max 1000 mg per dose). So lets update this rule. For 90 mg/kg/day of amoxicillin, use the following calculation:

   Weight in Pounds  x  20   =   mg dose of amoxicillin per dose

The other change is that this calculation is assuming 2x/day dosing (instead of 3x/day dosing). Let's go through an example. Assuming that you have a 10 pound child in your office, the calculation would look like this: 10 x 20 = 200. So this child would need 200 mg of amoxicillin 2x/day. Since amoxicillin comes in 400 mg per teaspoon, the child would need ½ teaspoon by mouth 2x/day.

The important thing to remember is that this calculation is PER DOSE (and NOT per day). Also, remember that this calculation only works for dosing amoxicillin 2x/day. Double check this calculation with your normal method of calculating the amoxicillin dose. I think you will find that they are pretty close!


Anonymous said...

How much 400 mg /5ml Amoxicililn should my 16lb get?

Anonymous said...

This doesn't make sense. If a child is 6o lbs x 20 = 1200mg, thats more than 2 grams per day of amoxicillin!

David Koo said...

Se post again: "Max 1000 mg per dose". Thanks!

Anonymous said...

What is the dose for a 20 pound child 2 x daily. Is it 400.

David Koo said...

Correct. If you wanted to dose amoxicillin at 90 mg/kg/day and the child weighted 20 pounds, then you would give approximately 400 mg of amoxicillin by mouth twice-a-day.

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