Isoniazid is an antibiotic primarily used to treat and prevent tuberculosis (TB), a serious infectious disease caused by the bacterium Mycobacterium tuberculosis. It works by inhibiting the growth of the bacteria, making it an essential part of TB treatment regimens. Typically taken as a pill or injection, isoniazid is often prescribed alongside other medications to enhance effectiveness and reduce the risk of drug resistance. Patients may need regular monitoring for side effects, as isoniazid can affect liver function and cause peripheral neuropathy if not managed properly.