Pediatric Antibiotic Dose and Volume Check
A 4-year-old child weighing 18.6 kg is admitted with an ear infection. The provider orders amoxicillin 45 mg/kg/day orally divided every 8 hours. The pharmacy supplies amoxicillin oral suspension 250 mg/5 mL. The parent reports giving one 5-mL teaspoon of the same suspension at home 6 hours ago, but cannot recall the prescribed dose. The home bottle label reads '7.5 mL every 8 hours,' and the bottle is nearly empty. The nurse must calculate the ordered dose per administration and the volume in mL, compare the home doses with the current order, and decide whether the next scheduled dose can be given as ordered. The medication administration record requires doses rounded to the nearest 0.1 mL. The child has no allergies, and renal function is normal.
1. Calculate the ordered dose in mg per administration and the corresponding volume in mL. Show each step.
Read the worked answer
Ordered daily dose: 18.6 kg × 45 mg/kg/day = 837 mg/day. Divided every 8 hours means three doses per day: 837 ÷ 3 = 279 mg per dose. The suspension is 250 mg/5 mL, which is 50 mg/mL. Volume per dose: 279 ÷ 50 = 5.58 mL, rounded to 5.6 mL. The calculation is dimensionally consistent: kg cancels in the first step, and mg cancels in the second. The nurse should not use the home label's 7.5 mL, because that volume would deliver 7.5 × 50 = 375 mg per dose, or 1,125 mg/day.
2. Compare the home doses with the current order. Should the nurse give the next scheduled dose as ordered? Explain the judgment.
Read the worked answer
Compare each home dose with the current order. The parent gave 5 mL, which is 5 × 50 = 250 mg. That is 29 mg less than the ordered 279 mg per dose. The home bottle label of 7.5 mL would be 375 mg per dose, which is 96 mg more than ordered, and 1,125 mg/day versus the ordered 837 mg/day. The current order is 45 mg/kg/day, while the label dose is about 60.5 mg/kg/day. The nurse should not give the next dose until the discrepancy is clarified, because the current provider order and the home label conflict. The nurse should verify the active prescription with the provider or pharmacy, document the home doses and the time of the last dose, and then administer the correctly calculated 5.6 mL if the current order is confirmed. The nurse should also assess timing: the last home dose was 6 hours ago, so the next dose is due in about 2 hours, not immediately.
3. If all three calculated doses are given each day, what is the daily volume and how many 100-mL bottles are needed for a 10-day course?
Read the worked answer
Daily volume at the calculated dose: 5.58 mL × 3 = 16.74 mL/day; using the rounded 5.6 mL gives 16.8 mL/day, so the nurse should base the bottle estimate on the unrounded amount to avoid shortage. For 10 days: 16.74 × 10 = 167.4 mL. A 100-mL bottle contains 100 mL, so one bottle is not enough; two bottles provide 200 mL. The nurse should document the calculation and ensure the family has enough suspension and a measuring device calibrated in mL, not a household teaspoon. If the pharmacy dispenses two 100-mL bottles, the remaining volume after the course is about 32.6 mL, which is appropriate buffer for loss or spillage. The nurse should also teach the parent to use the marked syringe.