Weight-Based (mg/kg) Dosing Practice
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Many drugs, especially in pediatrics, are dosed by body weight in mg/kg. The essential skills are converting pounds to kilograms and correctly distinguishing a total daily dose from a per-dose amount.
Formulakg = lb ÷ 2.2 • daily dose = mg/kg/day × weight • per dose = daily dose ÷ number of doses
Worked example
A 66 lb child on amoxicillin 45 mg/kg/day divided twice daily. kg = 66 ÷ 2.2 = 30 kg; daily = 45 × 30 = 1,350 mg; per dose = 1,350 ÷ 2 = 675 mg.
💡 mg/kg/DAY vs mg/kg/DOSE is the number-one trap in this family — read which one the order specifies.