# A nurse is preparing to administer liquid acetaminophen to a 6-year-old child who weighs 20 kg. The prescribed dose is 15 mg/kg every 6 hours. The medication concentration is 160 mg/5 mL. What is the correct volume to administer per dose?

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> subject: Pharmacology

## 문제

A nurse is preparing to administer liquid acetaminophen to a 6-year-old child who weighs 20 kg. The prescribed dose is 15 mg/kg every 6 hours. The medication concentration is 160 mg/5 mL. What is the correct volume to administer per dose?

## 보기

1. 1.5 mL
2. 7.5 mL
3. 9.4 mL **✔ 정답**
4. 12.5 mL

**정답: 3**

## 해설

Calculate dose: 20 kg × 15 mg/kg = 300 mg. Using concentration 160 mg/5 mL, volume = (300 mg × 5 mL) / 160 mg = 9.4 mL. Other options represent incorrect calculations.

## 심화 해설

Core Nursing Explanation
**Key Concept Analysis**: This question tests the fundamental nursing skill of pediatric medication dosage calculation. It requires a two-step process: first, calculating the total dose based on the child's weight and the prescribed mg/kg dose; second, converting that dose into a volume using the medication's concentration. This is a critical safety skill to prevent medication errors.

**Answer Rationale**: The correct answer is determined by following the calculation precisely.

**Step 1: Calculate the total dose per administration.**

Child's weight: 20 kg

Prescribed dose: 15 mg/kg

Total dose = 20 kg × 15 mg/kg = 300 mg

**Step 2: Calculate the volume to administer.**

Medication concentration: 160 mg / 5 mL

This means there are 160 mg of acetaminophen in every 5 mL of liquid.

To find the volume (mL) containing 300 mg, set up the proportion:

(300 mg / X mL) = (160 mg / 5 mL)

Cross-multiply: 160 mg × X mL = 300 mg × 5 mL

160X = 1500

X = 1500 / 160

X = 9.375 mL, which rounds to Key Point! 9.4 mL per dose.

**Distractor Analysis**:

Watch out for confusion!

• **Option 1 (1.5 mL)**: This is likely an error from miscalculating the dose per kg (e.g., 15 mg/kg for a 20 kg child is not 1.5 mL) or misplacing the decimal when using the concentration.

• **Option 2 (7.5 mL)**: This is a common trap. It results from using the concentration incorrectly. If you calculate 300 mg / 40 mg/mL (since 160 mg/5 mL simplifies to 32 mg/mL), you get 7.5 mL. However, 160/5 = 32, not 40. This option uses an incorrect concentration of 40 mg/mL.

• **Option 4 (12.5 mL)**: This might result from forgetting to divide by the concentration's strength. For example, (300 mg × 5 mL) = 1500, but then failing to divide by 160 mg.

**Related Concepts**: This calculation is a direct application of the "Desired Over Have" formula: (Desired Dose / Dose on Hand) × Volume on Hand. Here, Desired = 300 mg, Have = 160 mg, Volume = 5 mL. (300 mg / 160 mg) × 5 mL = 1.875 × 5 = 9.375 mL. Always double-check your calculations and have another nurse verify high-risk or pediatric medication doses.

Concept Summary
• **Weight-Based Dosing**: Essential for pediatric and some adult medications (e.g., chemotherapy, heparin).
• **Concentration**: Always check the label (e.g., 160 mg/5 mL, 325 mg/10.15 mL). Never assume.
• **Calculation Formula**: Dose (mg) = Weight (kg) × Dose per kg (mg/kg). Volume (mL) = [Dose (mg) / Concentration (mg per mL)].
• **Safety**: Key Point! Pediatric doses are especially sensitive to error. Always calculate independently and verify.

Side-by-Side Comparison!

| Calculation Error | What Went Wrong | How to Avoid |
| --- | --- | --- |
| Getting 7.5 mL | Used 40 mg/mL instead of 32 mg/mL (160/5). Mis-simplified the concentration. | Always write out the full concentration ratio (160 mg/5 mL) in your calculation. |
| Getting 1.5 mL | Decimal error or used 15 mg total dose instead of 300 mg. | Perform the weight × dose/kg multiplication first. Does 1.5 mL seem reasonable for a 20 kg child? Use clinical judgment. |
| Getting 12.5 mL | Multiplied dose by volume but forgot to divide by the concentration's mg amount. | Use the "Desired/Have x Volume" formula systematically every time. |

Anatomy, Physiology & Pharmacology Points
• **Acetaminophen (Tylenol)**: An analgesic (pain reliever) and antipyretic (fever reducer). It works by inhibiting prostaglandin synthesis in the CNS.
• **Pediatric Consideration**: Dosing is weight-based because children's metabolism and body surface area vary greatly. The maximum daily dose for acetaminophen is Key Point! typically 75 mg/kg/day, not to exceed 4,000 mg/day for older children/adults. For this child: 15 mg/kg q6h = 60 mg/kg/day, which is within the safe limit.
• **Liver Metabolism**: Acetaminophen is metabolized by the liver. Overdose can cause hepatotoxicity (liver damage).

Memory Tips
• **Formula Mnemonic**: "**D**ivide **D**esired by **H**ave, then **M**ultiply by **V**olume" (DDHMV) for the "Desired/Have x Volume" method.
• **Safety Check**: After calculating, ask: "Does this volume make sense?" For a 20 kg child, a dose of 1.5 mL seems too small, and 12.5 mL seems quite large for a liquid medication. 9.4 mL is a plausible volume.

High-Frequency NCLEX Topics
Medication calculation, especially pediatric and IV drip rates, is a **High Yield** topic on the NCLEX. The exam tests your ability to perform accurate calculations to ensure patient safety. You will see questions involving mg/kg dosing, unit conversions, and IV flow rates. Always show your work mentally and double-check.

Watch Out for Question Variations!
• The same concept could be tested by asking for the **total volume needed for 24 hours** (9.4 mL/dose × 4 doses/day = 37.6 mL/day).
• It could ask if the ordered dose is **safe** by comparing it to the maximum daily dose.
• The medication could change to **ibuprofen** or an **antibiotic** with a different concentration.
• The route could change to **IV**, requiring calculation of mg then conversion to mL based on an IV bag concentration.

## 임상 시나리오

Nursing Clinical Practice Guide
**Clinical Scenario**: You are a nurse on a pediatric unit. A 6-year-old patient, Jamie, was admitted with a fever and pain post-tonsillectomy. The physician orders acetaminophen 15 mg/kg PO q6h PRN for pain/fever. Jamie weighs 20 kg. You retrieve the bottle of liquid acetaminophen from the Pyxis, and the label reads "160 mg/5 mL."

**Nursing Intervention Strategy**:
1.  **Assessment**: Verify the order is complete (drug, dose, route, frequency). Confirm Jamie's weight in the chart. Assess pain level using an age-appropriate scale (e.g., FACES scale) and check temperature.
2.  **Calculation & Verification**: Perform the calculation as shown. Key Point! It is a best practice and often a policy to have a second nurse independently calculate and verify the dose for pediatric medications. Both nurses should initial the medication administration record (MAR).
3.  **Preparation**: Use an oral syringe (not a household teaspoon) for accurate measurement. Draw up 9.4 mL.
4.  **Administration**: Approach Jamie calmly. Explain what the medicine is for in simple terms. Administer the medication. For a child, you might mix it with a small amount of juice or applesauce if allowed and if the child has difficulty, ensuring the entire dose is taken.
5.  **Education**: Educate the parents on the dose, frequency, and the importance of using the measuring device that comes with the medication, not kitchen spoons. Warn them about other products containing acetaminophen to avoid accidental overdose.
6.  **Evaluation**: Reassess pain and temperature about 30-60 minutes after administration to evaluate effectiveness.

**Patient Safety and Precautions**:
• **Double-Check**: The "Five Rights" of Medication Administration (Right patient, drug, dose, route, time) are non-negotiable. For pediatrics, add "Right weight" and "Right calculation."
• **Hepatotoxicity**: Monitor for signs of overdose (nausea, vomiting, malaise, right upper quadrant pain). The antidote for acetaminophen overdose is N-acetylcysteine (NAC).
• **Concentration Confusion**: Acetaminophen comes in multiple concentrations (e.g., infant drops 160 mg/5 mL, children's suspension 160 mg/5 mL, junior strength 160 mg/5 mL may be different volumes). **Always read the label.**

Nursing Procedure & Medication Flow
**Step-by-Step for Oral Liquid Medication Administration:**
1.  Check provider's order and MAR.
2.  Perform hand hygiene.
3.  Obtain correct medication and verify concentration.
4.  Calculate dose and have a second nurse verify (for pediatrics/high-risk drugs).
5.  Draw up medication in an oral syringe to the exact volume.
6.  Identify the patient using two identifiers (name and date of birth).
7.  Explain the procedure to the child/parent.
8.  Administer the medication. For a child, place the syringe along the inside of the cheek and administer slowly to prevent choking.
9.  Offer a chase of water or juice if appropriate.
10. Document administration immediately: drug, dose, route, time, and your signature.
11. Monitor for therapeutic effect and adverse reactions.

A Word from Your Senior Nurse
"Med math can be intimidating, but it's the bedrock of safe nursing practice. In the real world, you'll have calculators and colleagues to double-check, but you must build the foundational skill and confidence. When you see a pediatric dose, your internal alarm should go off: 'Check the weight, check the concentration, calculate twice.' That moment of careful calculation is you being your patient's advocate and protector. On the NCLEX, they're testing not just your math skill, but your commitment to safety. Take a deep breath, write down your steps, and trust your process. You've got this!"

## 핵심 개념

- **Weight-Based Dosing** — Calculating medication dosage based on the patient's body weight (mg/kg), essential for pediatric, chemotherapy, and critical care medications to ensure safety and efficacy.
- **Concentration** — The amount of drug (mass) present in a given volume of solution (e.g., 160 mg/5 mL). Must be verified on the medication label before every calculation.
- **Desired Over Have Formula** — A standard medication calculation method: (Desired Dose / Dose on Hand) x Volume on Hand = Volume to Administer. A systematic approach to prevent errors.
- **Five Rights of Medication Administration** — A fundamental safety framework: Right Patient, Right Drug, Right Dose, Right Route, Right Time. Often expanded to include Right Documentation and Right Reason.
- **Acetaminophen** — A common analgesic and antipyretic. Risk of hepatotoxicity with overdose. Maximum daily dose is critical to monitor, especially in children (typically 75 mg/kg/day, max 4,000 mg).

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