Which of the following medications should be administered over a longer period to evaluate its effectiveness?

Isoniazid is an antibiotic commonly used in the treatment of tuberculosis (TB). To effectively evaluate its effectiveness, it is important to administer it over a longer duration. This is because the treatment regimen for active tuberculosis typically lasts for at least six months, often extending to nine months or longer depending on the patient's response and specific circumstances.

The effectiveness of isoniazid in treating TB is not immediately apparent; it takes time for the medication to exert its full effect on the bacteria. Monitoring the patient's clinical response, as well as performing follow-up imaging and lab tests, is essential during this prolonged treatment period to determine if the infection is resolving.

In contrast, medications like acetylcysteine, clarithromycin, and nizatidine may be used for shorter durations or can show effectiveness more rapidly, which is why they are not prioritized for longer evaluation periods in this context.