# 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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> subject: Pharmacology

## 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

Core Nursing Explanation
**Key Concept Analysis**: This question tests the critical nursing skill of pediatric medication calculation. It requires a multi-step process: 1) calculating the total daily dose based on weight, 2) dividing that total into the prescribed number of doses, and 3) converting the dose in milligrams to the volume in milliliters using the available concentration. Pediatric dosing is almost always weight-based to ensure safety and efficacy.

**Answer Rationale**: Let's break down the calculation step-by-step:

1. **Total Daily Dose**: Child's weight (18 kg) × Prescribed dose (40 mg/kg/day) = 720 mg/day.

2. **Single Dose Amount (mg)**: Total daily dose (720 mg/day) ÷ Number of doses per day (3) = 240 mg/dose.

3. **Dose Conversion to Volume (mL)**: We have a suspension of 250 mg per 5 mL. The amount to give is calculated by setting up a proportion: (250 mg / 5 mL) = (240 mg / X mL). Solving for X: X = (240 mg × 5 mL) / 250 mg = (1200 / 250) = 4.8 mL.

Key Point! The correct answer is **4.8 mL**, which corresponds to choice ③.

**Distractor Analysis**:

Watch out for confusion!

• **Choice ① (2.4 mL)**: This is half of the correct answer. A common error is forgetting to divide the total daily dose by the number of doses, or incorrectly using the concentration (e.g., 240 mg / (250 mg/5 mL) but miscalculating).

• **Choice ② (3.6 mL)**: This might result from an error in the weight-based calculation (e.g., using 20 mg/kg/day instead of 40 mg/kg/day) or a mistake in the final division step.

• **Choice ④ (7.2 mL)**: This is a critical error. This volume represents the total daily dose in milliliters (720 mg → (720×5)/250 = 14.4 mL/day; 14.4/2 = 7.2). This mistake could occur if the nurse administers the total daily dose in two doses instead of three, or confuses the single dose with the daily volume. Administering this amount would be an overdose.

**Related Concepts**: This calculation reinforces the "right dose" of the Five Rights of Medication Administration. For pediatric suspensions, always shake the bottle well to ensure even distribution of medication. Doses should be measured with an oral syringe, not a household teaspoon, for accuracy.

Concept Summary
• **Pediatric Dosing**: Typically weight-based (mg/kg).
• **Calculation Steps**: 1) Weight × Dose/kg = Total Daily Dose; 2) ÷ Doses/day = Dose per administration (mg); 3) Use concentration to convert mg to mL.
• **Safety**: Double-check calculations, use proper measuring devices, and verify the order is appropriate for the child's weight and condition.

Side-by-Side Comparison!

| Calculation Error | Resulting Dose | Why It's Wrong |
| --- | --- | --- |
| Forgot to divide by number of doses | Gives total daily dose as a single dose | Major overdose risk |
| Used wrong concentration (e.g., mg per mL) | Incorrect volume (often too high) | Dose inaccuracy |
| Miscalculated child's weight | Fundamentally wrong starting point | Entire calculation is invalid |

Anatomy, Physiology & Pharmacology Points
• **Amoxicillin**: A penicillin-class antibiotic. It is often prescribed for pediatric ear infections (otitis media), sinusitis, and pneumonia. It's available in suspensions because young children cannot swallow pills.
• **Pharmacokinetics in Children**: Children may metabolize drugs differently than adults. Weight-based dosing helps account for differences in body size and organ function (like liver and kidney maturity).

Memory Tips
• Use the mnemonic **"WDC"** for the calculation order: **W**eight × Dose = Total, then **D**ivide by number of doses, then **C**onvert using concentration.
• Always write out your units (kg, mg, mL) and cancel them as you calculate to check your work.
• For the proportion: **What you HAVE (concentration) equals What you WANT (dose/volume)**: (Have mg / Have mL) = (Want mg / X mL).

High-Frequency NCLEX Topics
Medication calculation, especially for pediatric and IV fluids, is a **must-know** area for the NCLEX. Expect at least one or two calculation questions. The exam tests your ability to perform safe dose calculations and identify potentially dangerous errors. Always re-calculate and consider if the answer makes sense clinically (e.g., is 7.2 mL a reasonable volume for a single dose for a 4-year-old?).

Watch Out for Question Variations!
• The question could ask for the **total volume to dispense** for a 10-day course.
• It could change the **frequency** (e.g., "divided twice daily").
• It could provide the concentration differently (e.g., "125 mg/5 mL" or "400 mg/5 mL").
• It could be an **IV medication** calculation, adding steps for infusion time or drip rates.

## 임상 시나리오

Nursing Clinical Practice Guide
**Clinical Scenario**: You are a nurse in a pediatric clinic. A 4-year-old patient, Jamie, is prescribed amoxicillin for acute otitis media (AOM). The mother is anxious and says, "I'm never sure if I'm giving the right amount with that little syringe."

**Nursing Intervention Strategy**:
1. **Assessment & Verification**: Confirm Jamie's current weight. Verify the prescription (drug, dose, route, frequency, duration) with the provider's order. Check for any documented penicillin allergies.
2. **Calculation & Preparation**: Perform the calculation independently, then have a second nurse verify it, following facility policy. Shake the suspension vigorously for 10-15 seconds to mix the medication evenly.
3. **Administration & Education**:
• Draw up the correct dose (4.8 mL) using an oral syringe.
• Educate the parent: "It's important to use this syringe every time. A kitchen spoon isn't accurate. Give it three times a day, roughly every 8 hours, until all the medicine is gone, even if Jamie starts feeling better."
• Demonstrate how to give the medication: "Place the syringe along the inside of the cheek, toward the back, and push the plunger slowly."
4. **Evaluation & Follow-up**: Ask the parent to demonstrate drawing up the dose. Provide written instructions. Educate on completing the full course and watching for adverse effects like rash, diarrhea, or signs of an allergic reaction.

**Patient Safety and Precautions**:
• **Allergy Check**: Always ask about penicillin/amoxicillin allergy before the first dose. A rash could indicate a reaction.
• **Measuring Device**: Never dispense medication without an appropriate measuring device (oral syringe or dosing cup).
• **Storage**: Instruct to refrigerate the reconstituted suspension and discard after the number of days indicated on the label (usually 10-14 days).

Nursing Procedure & Medication Flow
**Step-by-Step for Safe Pediatric Oral Administration**:
1. **Right Patient**: Use two identifiers (name, date of birth).
2. **Right Medication**: Check the label three times: when taking from shelf, before drawing up, before administering.
3. **Right Dose**: *Calculate, calculate, calculate!* Double-check your math. 4.8 mL is the correct volume.
4. **Right Route**: Oral suspension.
5. **Right Time**: Every 8 hours.
6. **Right Documentation**: Record the medication given, dose, time, and any parent education provided.

A Word from Your Senior Nurse
"Medication math can feel stressful, but it's one of the most concrete ways we protect our patients. That moment of double-checking your calculation isn't a sign of doubt—it's a sign of a competent, safety-conscious nurse. In pediatrics, a small error in decimals can mean a big difference for a little body. When you get a calculation question on the NCLEX, slow down. Write out the steps. Your brain is your best tool. In real life, never be afraid to use a calculator and ask a colleague to verify. Safe practice is always a team effort!"

## 핵심 개념

- **Weight-Based Dosing** — Calculating medication dosage based on the patient's body weight (e.g., mg/kg), which is standard practice in pediatrics to ensure safety and efficacy.
- **Oral Suspension** — A liquid dosage form where drug particles are suspended in a liquid. It must be shaken well before each use to ensure an even distribution of medication.
- **The Five Rights of Medication Administration** — A fundamental safety framework: Right Patient, Right Drug, Right Dose, Right Route, Right Time. "Right Dose" is the focus of this calculation question.
- **Pediatric Pharmacokinetics** — The study of how a child's body absorbs, distributes, metabolizes, and excretes drugs, which differs from adults and necessitates weight-based or body-surface-area dosing.
- **Dose Calculation Proportion** — A mathematical method to convert a prescribed dose (mg) to an administration volume (mL) using the medication's concentration (mg/mL). Formula: (Have mg / Have mL) = (Want mg / X mL).

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