What is used as a diluent for BCG vaccine?

Bihar CHO - 2021

Pharmacology

Easy

Appeared in: Bihar CHO - 2021

Explanation

The BCG vaccine contains live attenuated bacteria (Mycobacterium bovis).
To maintain the viability of these live organisms, an isotonic solution is required for reconstitution.
Normal Saline (0.9% NaCl) is the specifically recommended isotonic diluent that preserves the integrity of the bacterial cells, ensuring vaccine efficacy.
Using any other diluent can damage the bacteria and render the vaccine ineffective.

Option A: Ringer's lactate, although an isotonic solution, is not the manufacturer-specified diluent for the BCG vaccine. Its different electrolyte composition (containing potassium and calcium) could potentially interfere with the vaccine's stability.
Option C: Dextrose solutions are sugar-based and are not isotonic in the same way as saline. They are not recommended for reconstituting BCG as they do not provide the correct osmotic environment to preserve the live bacteria.
Option D: Distilled water is hypotonic. If used to reconstitute the BCG vaccine, it would cause water to move into the bacterial cells via osmosis, leading to cell lysis (rupture) and inactivation of the vaccine. It also causes significant pain and irritation when injected.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Vaccine reconstitution and administration as background academic context rather than a clinical decision trigger.
Using the correct diluent is a critical patient safety measure. An incorrect diluent can lead to vaccine failure, meaning the patient is not protected against the disease, and may cause adverse local reactions.
The '4-hour rule' is a crucial nursing responsibility. Once reconstituted, the BCG vaccine must be used within 4 hours and kept cool and away from light. Any remaining vaccine must be discarded to prevent administration of a contaminated or sub-potent dose.
What if? If a nurse accidentally reconstitutes the BCG vaccine with distilled water and administers it, the vaccine would likely be ineffective. The nurse must immediately report the medication error, the patient will need to be monitored for adverse reactions, and revaccination will likely be required at a later date according to protocol.

How to Approach the Question

First, identify the keywords in the question: 'diluent' and 'BCG vaccine'.
This is a factual recall question that tests your knowledge of vaccine preparation.
Recall that BCG is a live attenuated bacterial vaccine.
Consider the physiological requirements for keeping live bacteria viable. They need an isotonic environment to prevent cell damage.
Evaluate the options: Normal saline is isotonic. Ringer's lactate is also isotonic but less common for this purpose. Dextrose is a sugar solution. Distilled water is hypotonic.
Eliminate distilled water immediately because it would cause cell lysis. Eliminate Dextrose as it's not a suitable medium.

Concept Tested & Keywords

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