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?
44 lb is 20 kg, so the child's dose is 20kg*40(mg/kg day) = 800 mg/day. That would require 10 ml of the solution per day, since 5 ml contains 400 mg of the active ingredient.
A 100 ml bottle would last 100 ml/10 ml/day = 10 days.
I will leave you to convert the 10 ml daily liquid mixture dose to teaspoons (tsp).
To calculate the tsp (teaspoon) dose and determine how many days the prescription will last, we need to follow a step-by-step process:
Step 1: Convert weight from pounds to kilograms.
To determine the weight in kilograms, divide the weight in pounds (44 pounds) by 2.205:
44 pounds ÷ 2.205 = 19.955 kg (rounded to three decimal places).
Step 2: Calculate the total daily dose in milligrams (mg).
Multiply the weight in kilograms (19.955 kg) by the prescribed dose per kilogram (40 mg):
19.955 kg × 40 mg = 798.2 mg per day.
Step 3: Calculate the total volume required for the prescription.
Divide the total daily dose (798.2 mg) by the concentration (400 mg/5 ml) to find the necessary number of milliliters (ml):
798.2 mg ÷ 400 mg/5 ml = 9.9775 ml per day.
Step 4: Determine the teaspoon dose.
Since 1 teaspoon is approximately equal to 5 ml, divide the required amount in ml (9.9775 ml) by 5 ml to obtain the teaspoon dose:
9.9775 ml ÷ 5 ml = 1.9955 tsp (rounded to four decimal places).
So, the tsp dose would be approximately 2 tsp.
Step 5: Calculate the number of days the prescription will last.
Divide the total volume required for the prescription (100 ml) by the daily volume (9.9775 ml) to find the number of days:
100 ml ÷ 9.9775 ml = 10.025 days (rounded to three decimal places).
Therefore, the prescription will last approximately 10 days.