A doctor ordered a drug dose 75 mg OD. You have 125 mg/1.2 ml Injection available then how many ml should be given to the patient?

Appeared in: NORCET 3 - 2022 (Shift-2)

Explanation

The correct volume is found using the standard formula for liquid medications: (Dose Required / Stock Strength) × Stock Volume.
Substituting the given values into the formula gives: (75 mg / 125 mg) × 1.2 mL.
The calculation simplifies to 0.6 × 1.2 mL, which results in 0.72 mL.

Option A: Administering 1.25 mL would deliver approximately 130 mg of the drug, which is a significant overdose compared to the prescribed 75 mg.
Option C: Administering 1.0 mL would deliver approximately 104 mg of the drug, which is an overdose.
Option D: Administering 0.6 mL would deliver only 62.5 mg of the drug, which is an underdose and would not provide the intended therapeutic effect.

Visual 1: Infographic - A clear visual breakdown of the drug calculation formula: (Desired Dose / Available Dose) x Quantity = Amount to Administer.
Visual 2: Image - A 1 mL tuberculin syringe with the 0.72 mL mark highlighted, demonstrating its suitability for measuring precise, small-volume doses.

Clinical Relevance

Nursing practice connection: Use the key finding related to Drug dosage calculation for injectable medications to guide bedside assessment, documentation, and the next nursing action.
Accurate dosage calculation is a fundamental nursing responsibility to prevent medication errors, which can lead to significant patient harm from either overdose or underdose.
For volumes less than 1 mL, a tuberculin (1 mL) syringe should always be used to ensure the most precise measurement and administration.
What if? If the available stock was 125 mg in a 2 mL vial instead of 1.2 mL, the calculation would be (75/125) * 2 = 1.2 mL. This highlights how the stock volume critically impacts the final amount to administer.

How to Approach the Question

Step 1: Identify the three key values from the question: the 'Desired' dose (75 mg), the 'Available' or 'Have' dose (125 mg), and the 'Quantity' or 'Volume' it comes in (1.2 mL).
Step 2: Recall the universal formula for drug calculation: (Desired / Have) × Quantity.
Step 3: Ensure the units for the desired and available doses are the same (both are in mg, so no conversion is needed).
Step 4: Substitute the values into the formula: (75 mg / 125 mg) × 1.2 mL.
Step 5: Perform the division first (75 ÷ 125 = 0.6), then the multiplication (0.6 × 1.2 = 0.72).
Step 6: Compare your calculated answer (0.72 mL) with the given options and select the match. Always double-check your math.

Concept Tested & Keywords

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Practise the full NORCET 3 - 2022 (Shift-2)

Attempt every question from this paper in a timed mock, then review the full solution for each one.