Only patients with active tuberculosis need antitubercular medication.
After someone tests positive for infection, he'll undergo additional tests to determine if tuberculosis has developed--usually a chest X-ray and, especially if the chest X-ray is abnormal, serial sputum testing. If these tests are negative, the doctor may prescribe a course of preventive medication for 6 to 12 months. This strategy greatly lowers the risk that tuberculosis will develop later. Treating exposure to multidrug-resistant tuberculosis is more complicated: The Centers for Disease Control and Prevention recommends using three to four anti tubercular agents at once.