The physician prescribed morphine sulphate 2 mg IV. The medication is available in a vial containing 10 mg/ml. How much of drug will you take from the vial?

Appeared in: RUHS, Jaipur, PB B.Sc Nursing Entrance-2019

Explanation

The standard formula for drug calculation is (Desired Dose / Dose on Hand) × Volume.
The desired dose is 2 mg, and the dose on hand is 10 mg in 1 mL.
Plugging the values into the formula: (2 mg / 10 mg) × 1 mL.
The calculation results in 0.2 mL, which is the correct volume to administer.

Option A: Administering 0.1 mL would deliver only 1 mg of morphine (0.1 mL × 10 mg/mL), which is half the prescribed dose and would likely be ineffective for pain management.
Option C: Administering 0.5 mL would deliver 5 mg of morphine (0.5 mL × 10 mg/mL). This is 2.5 times the prescribed dose and constitutes a significant overdose, increasing the risk of severe adverse effects like respiratory depression.
Option D: Administering 0.6 mL would deliver 6 mg of morphine (0.6 mL × 10 mg/mL). This is three times the prescribed dose, a dangerous overdose that could lead to life-threatening complications.

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 dosage calculation is a critical nursing responsibility to ensure patient safety and prevent medication errors, especially with high-alert medications like opioids.
The 'Three Checks' and 'Rights of Medication Administration' must be performed before administering any drug. This includes checking the order, verifying the patient, and ensuring the correct drug, dose, route, and time.
What if? If the available vial was 5 mg/mL instead of 10 mg/mL, the calculation would be (2 mg / 5 mg/mL) = 0.4 mL. This highlights the importance of always verifying the medication concentration before calculating the dose.

How to Approach the Question

First, identify the key pieces of information: the desired dose (D), the dose on hand (H), and the volume the dose is in (V).
Recall the universal formula for drug calculation: Volume to administer = (Desired Dose / Dose on Hand) × Volume.
Substitute the values from the problem into the formula: (2 mg / 10 mg) × 1 mL.
Perform the mathematical calculation to find the correct volume.
Critically evaluate the answer. Since the desired dose (2 mg) is one-fifth of the available concentration (10 mg), the volume should be one-fifth of 1 mL, which is 0.2 mL.
Always double-check your calculation, preferably with another nurse, before administering a high-alert medication like morphine.

Concept Tested & Keywords

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

E6 Nursing Fundamentals Taylor p. 848-850

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