Medication Administration and Pharmacologic Principles
Medication questions are almost always about weight-based calculation, safe dose verification, and avoiding the classic pediatric errors.
Core rules
- Verify every order against a safe dose range in mg/kg (or mg/m² for chemotherapy) before administration.
- Pediatric pharmacokinetics differ: higher total body water, lower protein binding, immature hepatic enzymes and glomerular filtration.
- Measure liquids in milliliters with an oral syringe; never use household teaspoons or tablespoons.
- Use leading zeros but never trailing zeros - 0.5 mg, not .5 mg or 5.0 mg.
- Acetaminophen 10–15 mg/kg every 4–6 hours, maximum 75 mg/kg/day; ibuprofen 10 mg/kg every 6–8 hours, maximum 40 mg/kg/day, only from 6 months.
- Codeine and tramadol are contraindicated under 12 years; aspirin is avoided in children.
- Infants receive vaccines in the vastus lateralis; toddlers and older children in the deltoid.
Worked example
An 8 kg infant is ordered acetaminophen 150 mg every 4 hours. Calculate the dose per kilogram: 150 ÷ 8 = 18.75 mg/kg, which exceeds the 15 mg/kg maximum of 120 mg. The interval also allows six doses daily, above the 75 mg/kg/day ceiling. Call the prescriber, propose 120 mg every 6 hours, and document the intervention. Checking the safe range - not just the arithmetic - is what prevents harm.
Traps
- Accepting an order that is arithmetically correct but outside the safe range.
- Decimal point errors and trailing zeros.
- Using an adult tablet or adult concentration.
- Adding potassium to IV fluids before urine output is established.