A forty-year-old patient is to be given 1200 Mg injection Ceftriaxone. What quantity of medicine should be given to the patient? (1 vial = 1 gram for injection is to be dissolved in 10 ml of water)

1. A

   8 ml

2. B

   10 ml

3. C

   12 ml

4. D

   14 ml

Appeared in: MP CHO - 2022

Explanation

• The core task is to calculate the volume of medication needed based on the prescribed dose and the available concentration after reconstitution.
• First, convert the available dose from grams to milligrams: 1 gram = 1000 mg.
• Next, determine the concentration of the solution: 1000 mg is dissolved in 10 ml of water, resulting in a concentration of 100 mg/ml.
• Finally, apply the dosage calculation formula: (Dose Required / Dose Available) × Volume = (1200 mg / 1000 mg) × 10 ml = 12 ml.
• Alternatively, using the concentration: Volume = Dose Required / Concentration = 1200 mg / 100 mg/ml = 12 ml.

Why Other Options Were Wrong

• Option A: Administering 8 ml would deliver only 800 mg of Ceftriaxone (8 ml × 100 mg/ml), which is an underdose of 400 mg.
• Option B: Administering 10 ml would deliver 1000 mg of Ceftriaxone (10 ml × 100 mg/ml), which is an underdose of 200 mg. This error occurs if the nurse administers the entire contents of the vial without calculating the specific dose required.
• Option D: Administering 14 ml would deliver 1400 mg of Ceftriaxone (14 ml × 100 mg/ml), which is an overdose of 200 mg.

Related Visual

• Visual 1: Infographic - A step-by-step visual guide showing the formula for drug dosage calculation: (Dose Required / Dose on Hand) x Quantity = Amount to Administer. This helps in visualizing the components of the calculation.
• Visual 2: Diagram - An illustration of a vial and a syringe, showing the process of reconstituting a powder and drawing up the calculated dose, reinforcing the practical steps involved.

Clinical Relevance

• Nursing practice connection: Use the key finding related to Drug Dosage Calculation to guide bedside assessment, documentation, and the next nursing action.
• Accurate dosage calculation is a fundamental nursing responsibility and is critical for patient safety. Errors can lead to therapeutic failure (underdosing) or toxicity (overdosing).
• This skill is directly tied to the 'Right Dose' principle of the 'Five Rights of Medication Administration'.
• What if the medication was to be given intramuscularly (IM)? The nurse must consider the maximum volume for a single IM injection site (typically 3-5 mL for a large muscle in an adult). A 12 ml dose would need to be split into multiple injections at different sites to prevent tissue damage and ensure absorption.

How to Approach the Question

• First, identify the key numbers in the problem: the required dose (1200 mg), the available dose (1 gram), and the volume it's dissolved in (10 ml).
• Second, ensure all units are consistent. Convert the available dose from grams to milligrams (1 g = 1000 mg).
• Third, determine the concentration of the drug per ml. Divide the total amount of drug (1000 mg) by the total volume (10 ml) to get mg/ml.
• Finally, use the standard dosage calculation formula: (Required Dose / Concentration) to find the volume in ml to administer.

Concept Tested & Keywords

• Concept Tested: Drug Dosage Calculation
• Stem keywords: Ceftriaxone, 1200 Mg, injection, 1 gram, 10 ml
• Lead-in keywords: What quantity
• Clinical cues: Reconstitution of a powdered drug is required, which adds a step to the calculation process.

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QFP_9nn77A8SGKjF9Frjzd

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