Digoxin (lavoxin) 0.125 mg is ordered. It is available in a dose vial 500 mcg/mL. How many mL does the nurse administer?

Appeared in: NVS- 2025

Explanation

The first step is to convert the ordered dose to the same unit as the available concentration. The ordered dose is 0.125 mg, which converts to 125 mcg (0.125 × 1000).
The medication is available at a concentration of 500 mcg/mL.
Using the formula (Dose Ordered / Dose on Hand) × Quantity:
(125 mcg / 500 mcg/mL) × 1 mL
The calculation (125 ÷ 500) results in 0.25, meaning the nurse should administer 0.25 mL.

Option A: 5 mL is incorrect. This volume would be administered if the ordered dose was 75 mcg, based on an assumed concentration of 50 mcg/mL.
Option B: 5 mL is incorrect. This volume would be administered if the ordered dose was 175 mcg, based on an assumed concentration of 50 mcg/mL.
Option D: 2 mL is incorrect. This volume would be administered if the ordered dose was 100 mcg, based on an assumed concentration of 50 mcg/mL.

Clinical Relevance

Nursing practice connection: Knowing Drug Dosage Calculation helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
Accurate medication calculation is a critical nursing skill to prevent medication errors and ensure patient safety. Errors with high-alert medications like Digoxin can have severe consequences.

Digoxin has a narrow therapeutic index (0.5-2 ng/mL), meaning the margin between a therapeutic dose and a toxic dose is very small. This makes precise dosing essential.
Always double-check calculations, especially for high-alert medications. Many facilities require a second nurse to verify calculations for drugs like Digoxin.
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How to Approach the Question

First, identify the key information: the ordered dose (0.125 mg) and the available concentration (500 mcg/mL).
Recognize that the units (mg and mcg) are different and a conversion is necessary. Convert the ordered dose to match the unit of the available concentration.
Apply the standard dosage calculation formula: (Dose Ordered / Dose on Hand) x Quantity.
Perform the calculation. If the result does not match any option, re-read the question carefully to check for potential typos. In this case, the concentration is likely a typo (50 instead of 500).
Calculate the answer based on the most plausible correction that matches an option.
Select the option that corresponds to your calculated volume.

Concept Tested & Keywords

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E6 Nursing Fundamentals Taylor p. 848-850

E6 Nursing Fundamentals Potter Perry 12e Part 3 p. 142-144

E6 Pharmacology Nursing Lilley 11e Part 2 p. 77-79

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