Dosage By Weight Questions

Given the weight of a patient and a dosage specified in terms of weight, calculate the necessary dosage. These problems are a type of pediatric dosage calculations.

Formula:
Weight in Kg * Dosage Per Kg  =  Y (Required Dosage)

Example: A doctor orders 200 mg of Rocephin to be taken by a 15.4 lb infant every 8 hours. The medication label shows that 75-150 mg/kg per day is the appropriate dosage range. Is this doctor's order within the desired range?
Weight in Kg * Dosage Per Kg  =  Y (Required Dosage)
Convert 15.4 lb to kg.
  • lb → kg    ( ÷ by 2.2 )
  • 15.4 lb ÷ 2.2 = 7 kg
7 kg * 75 mg/kg  =  525 mg (Minimum Desired Dosage)
7 kg * 150 mg/kg  =  1,050 mg (Maximum Desired Dosage)
24 hours in one day and the medication is ordered every 8 hours.
  • 24 hrs / 8 hrs = 3 times per day doctor ordered medication
  • 200 * 3 = 600 mg ordered per day
  • 600 mg is within the desired range of 525-1,050 mg
Yes doctor has ordered a dosage within the desired range.

Example: Solumedrol 1.5 mg/kg is ordered for a child weighing 74.8 lb. Solumedrol is available as 125 mg / 2mL. How many mL must the nurse administer?
Weight in Kg * Dosage Per Kg  =  Y (Required Dosage)
Convert 74.8 lb to kg.
  • lb → kg    ( ÷ by 2.2 )
  • 74.8 lb ÷ 2.2 = 34 kg
34 kg * 1.5 mg/kg  =  51 mg
Ordered
Have
x Volume Per Have  =  Y (Liquid Required)
51 mg
125 mg
x 2 mL  =  0.82 mL



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