Which of the following is the drug of choice for prophylaxis against diphtheria?

UP NHM CHO 7 Sept 2022(shift-1st)

Pharmacology

Easy

Appeared in: UP NHM CHO 7 Sept 2022(shift-1st)

Explanation

Erythromycin is a recommended first-line antibiotic for the prophylaxis of diphtheria in close contacts of an infected person.
It is highly effective for eradicating Corynebacterium diphtheriae from the nasopharynx, which is crucial for managing asymptomatic carriers and preventing further spread.
The standard prophylactic regimen involves a 7 to 10-day course of oral erythromycin.
Its mechanism of inhibiting bacterial protein synthesis also halts the production of the diphtheria toxin, adding to its therapeutic benefit.

Option A: Amoxicillin is a penicillin-class antibiotic. While injectable forms like Penicillin G are used to treat active diphtheria, Erythromycin is generally preferred for prophylaxis and for eradicating the carrier state.
Option C: Ciprofloxacin is a fluoroquinolone antibiotic. This class of drugs is not indicated for the treatment or prophylaxis of infections caused by Corynebacterium diphtheriae.
Option D: Cotrimoxazole is a combination of two antibiotics (trimethoprim and sulfamethoxazole). It is not effective against C. diphtheriae and has no role in its management.

Clinical Relevance

Nursing practice connection: Knowing Pharmacology: Prophylaxis for Diphtheria helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
Nurses are responsible for identifying and managing close contacts of diphtheria patients to prevent outbreaks. This includes administering prophylactic antibiotics as prescribed.
Patient education is critical. The nurse must emphasize the importance of completing the full 7-10 day course of Erythromycin to ensure the bacteria are completely eradicated and prevent the development of a chronic carrier state.
What if? If a close contact is allergic to Erythromycin, the recommended alternative is a single intramuscular injection of benzathine penicillin G, assuming the person does not have a penicillin allergy.

How to Approach the Question

First, identify the key components of the question: it asks for the 'drug of choice' for 'prophylaxis' (prevention) of 'diphtheria'.
Recognize this as a factual recall question based on established public health and pharmacology guidelines for communicable diseases.
Differentiate between the treatment of an active disease and prophylaxis for an exposed contact. Prophylaxis aims to prevent the disease from developing in someone who has been exposed.
Systematically evaluate the antibiotic options provided. Recall or deduce the primary uses for each.
Erythromycin (a macrolide) is a standard choice for prophylaxis of several respiratory infections, including diphtheria and pertussis.
Amoxicillin (a penicillin) is a broad-spectrum antibiotic, but specific forms of penicillin (like Penicillin G) are used for treatment, and Erythromycin is often preferred for prophylaxis/carrier eradication.

Concept Tested & Keywords

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E6 Medicine Harrison 22e Part 1 p. 1265-1267

E6 Nelson Textbook of Pediatrics(2024) — Volume 1 p. 1732-1734