CalculatingDosagesforInfantsandChildrenUsingBodyWeight
Pediatric patients’ dosages must be carefully calculated based on body weight. It is important to pay
close attention to the client's weight, prescription, and frequency of the medication instructions.
Example1:
An infant is admitted with an infection and weighs 3.6 kg. Ampicillin 250 mg/kg/day, IV divided
every 8 hours. Calculate the dosage (mg/dose) of ampicillin the patient should receive. Round the
answer to the nearest whole number.
Step One: set up the problem using dimensional analysis, solving for mg/dose and converting day to
hours.
mg kg/dayx3.6kg
dose=250mg 1x1day
24hours
Step Two: Solve for mg/dose, so you will need to solve the number of hours between doses every 8
hours or 3 doses per day. You can use either to solve the problem.
mg kg/dayx3.6kg
dose=250mg 1x1day
24hoursx8hour
dose=¿ 300mg/dose
OR
mg kg/dayx3.6kg
dose=250mg 1x1day
3doses=¿ 300mg/dose
a. The pharmacy supplies ampicillin. Using the previous answer and the label below,
determine the mL of medication the nurse will administer per dose. Round to the nearest
tenth.
mL=mL
500mgx300mg
dose=0.6mL
Curriculum&Assessment
4/10/25
Pediatric patients’ dosages must be carefully calculated based on body weight. It is important to pay
close attention to the client's weight, prescription, and frequency of the medication instructions.
Example1:
An infant is admitted with an infection and weighs 3.6 kg. Ampicillin 250 mg/kg/day, IV divided
every 8 hours. Calculate the dosage (mg/dose) of ampicillin the patient should receive. Round the
answer to the nearest whole number.
Step One: set up the problem using dimensional analysis, solving for mg/dose and converting day to
hours.
mg kg/dayx3.6kg
dose=250mg 1x1day
24hours
Step Two: Solve for mg/dose, so you will need to solve the number of hours between doses every 8
hours or 3 doses per day. You can use either to solve the problem.
mg kg/dayx3.6kg
dose=250mg 1x1day
24hoursx8hour
dose=¿ 300mg/dose
OR
mg kg/dayx3.6kg
dose=250mg 1x1day
3doses=¿ 300mg/dose
a. The pharmacy supplies ampicillin. Using the previous answer and the label below,
determine the mL of medication the nurse will administer per dose. Round to the nearest
tenth.
mL=mL
500mgx300mg
dose=0.6mL
Curriculum&Assessment
4/10/25
