Ethambutol HCl is primarily used in the treatment of tuberculosis (TB), particularly in combination with other antitubercular drugs like isoniazid, rifampin, and pyrazinamide. It works by inhibiting the synthesis of the bacterial cell wall, effectively stopping the growth of Mycobacterium tuberculosis, the bacterium responsible for TB. This makes it a critical component in both the initial and continuation phases of TB therapy. It is especially valuable in cases of drug-resistant TB, where it helps to enhance the efficacy of the treatment regimen. Additionally, Ethambutol HCl is used in the prevention of TB in individuals who have been exposed to the disease but have not yet developed symptoms. Its ability to target the bacteria without significant interference with human cells makes it a relatively safe option for long-term treatment, though regular monitoring for potential side effects, such as optic neuritis, is essential.