Essentiality of INH in TB Therapy

Tuberculosis (TB) disease is caused by bacteria that have infected the lung. TB bacteria are very small living agents that are spread by coughing and can be killed by taking TB drugs. To kill these TB bacteria TB patients have to take a combination of four drugs for 2 months and then two drugs for a further 4 months. During the first 2 months patients take rifampicin, isoniazid, ethambutol, and pyrazinamide. After that patients take only isoniazid and rifampicin for a further 4 months, making a total of 6 months therapy. In A5307 the investigators wanted to test a new combination of drugs to see if the investigators could treat TB faster in the future. Studies in animals have suggested that one of the four drugs, isoniazid, only works for a few days and may not be needed after the first two doses of TB treatment to kill the TB bacteria. After that its effects wear off to the point that it may even interfere with the other drugs. The investigators wanted to see if stopping isoniazid early, or using moxifloxacin, a different drug, instead could treat TB faster. This study was the first time that this type of regimen without isoniazid had been tested in humans. If the investigators could show that isoniazid stops working after a few days, the investigators could then try to see if they could possibly make a better tuberculosis treatment in the future.