# A nurse is preparing to administer amoxicillin to a 4-year-old child who weighs 18 kg. The prescribed dose is 40 mg/kg/day divided into three equal doses. The available medication is amoxicillin oral suspension 250 mg/5 mL. How many milliliters should the nurse administer for each dose?

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## 문제

A nurse is preparing to administer amoxicillin to a 4-year-old child who weighs 18 kg. The prescribed dose is 40 mg/kg/day divided into three equal doses. The available medication is amoxicillin oral suspension 250 mg/5 mL. How many milliliters should the nurse administer for each dose?

## 보기

1. 2.4 mL
2. 3.6 mL
3. 4.8 mL **✔ 정답**
4. 7.2 mL

**정답: 3**

## 해설

The correct dose is 4.8 mL, calculated as (18 kg × 40 mg/kg/day ÷ 3 doses) × (5 mL / 250 mg). Other options result from errors in weight-based calculation, dose division, or concentration conversion.

## 심화 해설

Understanding the Prescription

The first step in any pediatric dosage calculation is to clearly identify the prescribed daily dose. The order states amoxicillin 40 mg/kg/day. For a child weighing 18 kg, the total amount of medication needed per day is calculated by multiplying the weight by the dose per kilogram.

Calculating the Total Daily Dose

Total daily dose = 40 mg × 18 kg = 720 mg. This means the child must receive a total of 720 mg of amoxicillin over the course of the day.

Determining the Single Dose

The prescription specifies that this total daily amount is to be divided into three equal doses. To find the amount for one single dose, divide the total daily dose by 3.

Single dose = 720 mg / 3 = 240 mg. The nurse must administer 240 mg of amoxicillin for each dose.

Converting the Dose to Volume

The medication available is an oral suspension with a concentration of 250 mg per 5 mL. This ratio is used to convert the required mass (240 mg) into the volume to be drawn up and administered. Using the formula (Desired dose / Available dose) × Available volume:

Volume per dose = (240 mg / 250 mg) × 5 mL = 0.96 × 5 mL = 4.8 mL.

Clinical Significance of Accurate Calculation

The result of 4.8 mL per dose is the precise volume the nurse should administer. Mastery of medication dosage calculation (MDC) is a non-negotiable clinical skill, as highlighted in research on healthcare education. A randomized quasi-experimental study by Baran and Öztürk (2025) emphasizes that MDC is a vital component of clinical competence, where miscalculations can lead to life-threatening outcomes [1]. This principle is especially critical in pediatric populations, where doses are weight-based and errors can have amplified consequences. The prescription of antibiotics like amoxicillin must be precise not only for therapeutic efficacy but also to support antimicrobial stewardship. Inappropriate dosing, whether subtherapeutic or excessive, can contribute to the development of antimicrobial resistance (AMR), a significant global health challenge addressed in clinical practice guidance for children . Ensuring the calculated volume of 4.8 mL is accurately drawn and administered is a direct application of safe prescribing quality, a key factor in combating AMR and ensuring positive patient outcomes . The process of verifying the total daily dose (720 mg) and the single dose (240 mg) before the final volume conversion is a critical safety checkpoint that prevents potentially harmful tenfold errors.References (research sources)

- [1]The effects of video-based and blended learning on medication dosage calculation skills of paramedic students: A randomized, quasi-experimental study.RCT/clinical trialBaran L, Öztürk H. (2025) · DOI: 10.1097/md.0000000000043651

## 임상 시나리오

Pediatric Oral Amoxicillin Dose CalculationWeight-Based Dosing to Volume Conversion
Calculate the total daily dose by multiplying the child's weight (18 kg) by the prescribed dose (40 mg/kg/day), resulting in 720 mg/day.

Divide the total daily dose by the number of doses per day (3) to find the single dose: 240 mg.

Convert the mass dose to volume using the Desired Over Have formula: (240 mg / 250 mg) × 5 mL = 4.8 mL per dose.

CautionAlways shake the oral suspension vigorously before drawing up the dose to ensure uniform drug distribution. Verify the concentration on the bottle label against the order.

## 핵심 개념

- **Weight-Based Dosing** — A method of calculating medication doses for pediatric patients based on body weight in kilograms (mg/kg).
- **Desired Over Have Formula** — A universal formula for dosage calculation: (Desired dose / Available dose) × Available volume = Volume to administer.
- **Oral Suspension** — A liquid medication form containing fine, undissolved particles that must be shaken well before administration to ensure uniform dose delivery.

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