Posted by **Arlene** on Tuesday, August 16, 2011 at 5:03pm.

A prescription calls for erythromycin 400mg/5ml, dispense 100ml. The dose is 40mg/kg/day and the child weighs 44 pounds. The si. reds ? tsp qid until gone. How many tsp and how many days will the prescription last?.

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**bobpursley**, Tuesday, August 16, 2011 at 5:45pm
40mg/kg*1kg/2.2 lbs*44lbs=800mg/day. Assume each tsp contains 5ml which is very close to 5grams, or 400mg per tsp.

so to get 800mg/day, you need 1/2 tsp 4x a day. It will last....100ml/10tsp*5ml/tsp=4 days.

check me on this.

- health -
**bobpursley**, Tuesday, August 16, 2011 at 5:47pm
oops 100/50 is two days. Goodness. I will get someone to check this, a smart nurse would help.

- health -
**Dr Sarah**, Tuesday, August 16, 2011 at 8:38pm
Actually, you are right in your calculation of 1/2 tsp 4 times a day. But that means you will use a total of 2 teaspoons per day. 1 tsp is 5ml so that means 10ml used per day. If there is 100ml in the bottle, then this is a 10 day supply. (100ml÷10ml/day)

- health -
**bobpursley**, Tuesday, August 16, 2011 at 10:06pm
thanks, Dr Sarah.

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