**Question:** Dosage of topical tobramycin eye drops:

A. 1 drop 4 times a day
B. 2 drops 4 times a day
C. 3 drops 4 times a day
D. 1 drop 6 times a day

**Core Concept:**
Tobramycin is an aminoglycoside antibiotic used for the treatment of ocular infections caused by susceptible bacteria, particularly in cases of severe infections or when other antibiotics are ineffective. It works by inhibiting bacterial protein synthesis and ultimately leading to bacterial cell death.

**Why the Correct Answer is Right:**
The correct answer is **A. 1 drop 4 times a day**. Tobramycin eye drops are administered at regular intervals throughout the day to ensure a continuous therapeutic concentration in the ocular environment. Using a lower frequency (6 times a day, option D) may result in suboptimal drug levels, leading to ineffective treatment or even resistance development. Frequent administration (4 times a day, option B) might cause excessive exposure to the drug, potentially causing toxicity and ocular surface damage. Therefore, the optimal choice is 4 times a day (option A), maintaining an appropriate balance between therapeutic efficacy and safety.

**Why Each Wrong Option is Incorrect:**

**Option B (2 drops 4 times a day):**
Administering two drops instead of one (option A) increases the total drug concentration but does not guarantee better efficacy. In fact, it might lead to excessive drug exposure and toxicity.

**Option C (3 drops 4 times a day):**
Using three drops per administration (option C) is more than the optimal dose (1 drop) and may result in increased toxicity and ocular surface damage.

**Option D (1 drop 6 times a day):**
Increasing the frequency of administration (6 times a day) while using the same dose (1 drop) does not guarantee better efficacy and may cause suboptimal drug levels, potentially leading to treatment failure or resistance development.

**Clinical Pearl:**
When prescribing topical medications, it is essential to consider the balance between drug exposure and safety. In the case of tobramycin eye drops, the optimal dosing depends on the severity of the infection and the patient's individual response. Regular monitoring and adjustment of the dosage and frequency are crucial to achieve the best outcome while minimizing side effects.