A prescription calls for ....?

Question

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

Answer 1

The child weighs 44 pounds, which converts to 20kg. You have to multiply the dose of 40mg/kg/day by 20 kg to get 800mg total per day. If you are giving 400mg/5ml (5ml = 1 teaspoon), and you are giving it QID, then 800mg/4 times a day = 200mg per dose. In other words, you need to give 1/2 teaspoon QID until gone. If you dispense 100ml, this will give you 8000mg total, and it will last 10 days. Sorry if this is confusing, I'm bad at explaining things! :) Hope it helps!