Practice Question
A patient is prescribed 8 mg of a medication. The medication is available in 20 mg/mL concentration. How many milliliters should the nurse administer?
Answer Choices:
Correct Answer:
0.4 mL
Rationale:
0.4 mL
🔹 To determine how many milliliters to administer, the nurse must use the formula:
Dose needed ÷ Dose on hand (per mL).
🔹 The desired dose is 8 mg, and the concentration is 20 mg per 1 mL.
🔹 The nurse calculates: 8 mg ÷ 20 mg/mL = 0.4 mL, which is the exact amount required.
🔹 This dose ensures the patient receives the correct therapeutic amount of medication without risking underdose or overdose.
🔹 Therefore, 0.4 mL is the accurate and safe volume to administer based on the ordered dose and supplied concentration.
2 mL
🔹 Administering 2 mL at a concentration of 20 mg/mL delivers 40 mg, which is five times the ordered dose of 8 mg.
🔹 This would constitute a dangerous medication overdose, significantly exceeding safe therapeutic ranges.
🔹 Giving such an excessive dose could place the patient at risk for severe adverse effects depending on the drug class.
🔹 This incorrect answer reflects a misunderstanding of proportional calculations involving mg per mL.
🔹 Therefore, 2 mL is unsafe and unrelated to the correct mathematical conversion.
1.5 mL
🔹 Administering 1.5 mL equals 30 mg of medication, far above the prescribed 8 mg dose.
🔹 This represents nearly a four-fold overdose, which could lead to toxic effects.
🔹 Choosing this answer indicates confusion between desired dose and available concentration.
🔹 Accurate dimensional analysis clearly shows that 1.5 mL delivers much more medication than needed.
🔹 Thus, 1.5 mL is not appropriate for the ordered dose.
0.8 mL
🔹 At 20 mg/mL, 0.8 mL contains 16 mg, which is double the required 8 mg dose.
🔹 This incorrect volume would cause a significant dosing error and violates safe medication administration principles.
🔹 It shows misapplication of the proportion calculation, likely from dividing incorrectly or doubling the desired dose inadvertently.
🔹 Even small extra doses may cause harm depending on the drug’s potency.
🔹 Therefore, 0.8 mL is not a correct or safe option.
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This question is from Custom Dosage Calculation. which contains 42 questions.
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Question Details
- Category: RN Nursing Exam(s)
- Subcategory: ATI Exam(s)
- Domain: RN ATI Dosage Calculations
- Answer Choices: 4