An infant weighs 8 lbs and has an order for amoxicillin 45 mg/kg/day in divided doses every 12 hours. How many milligrams will you administer for each dose?
The correct answer and explanation is:
To calculate how many milligrams of amoxicillin should be administered per dose, follow these steps:
Step 1: Convert the infant’s weight to kilograms
Since the infant’s weight is given in pounds, convert it to kilograms. The conversion factor is:
1 pound = 0.453592 kilograms.
For an 8-pound infant: 8 lbs×0.453592 kg/lb=3.629 kg8 \, \text{lbs} \times 0.453592 \, \text{kg/lb} = 3.629 \, \text{kg}
Step 2: Calculate the total daily dose
The prescribed dosage is 45 mg of amoxicillin per kilogram of body weight per day. To find the total daily dose for the infant, multiply the infant’s weight by the prescribed dose: 45 mg/kg/day×3.629 kg=163.305 mg/day45 \, \text{mg/kg/day} \times 3.629 \, \text{kg} = 163.305 \, \text{mg/day}
Step 3: Divide the daily dose into two doses
The medication is to be given in divided doses every 12 hours, meaning two doses per day. To find the amount per dose, divide the total daily dose by 2: 163.305 mg/day2=81.6525 mg/dose\frac{163.305 \, \text{mg/day}}{2} = 81.6525 \, \text{mg/dose}
Step 4: Round the dose to a practical value
Since 81.6525 mg is not a standard tablet size, it can be rounded to 81.7 mg for ease of administration.
Final Answer:
The infant should be administered 81.7 mg of amoxicillin every 12 hours.
Explanation:
This calculation ensures the infant receives the prescribed dose based on weight and frequency, while also considering practical aspects like the rounding of milligram amounts for easier dosing. Adjustments might be needed depending on available concentrations of the medication or further instructions from the healthcare provider.