What Are the Treatments for Drug Resistant TB?

Drug-resistant tuberculosis is a term for strains of the TB germ that have become immune to the effects of standard drugs used to treat the infection. Such drug resistance makes the infection more difficult to treat because the first-line drugs no longer do any good. Second- and third-line medications can be used, but they frequently don't work as well, and they pose a higher risk of side effects. Tuberculosis that's resistant to multiple drugs must be treated for a longer period--sometimes years-and still, its cure rate is only 50 percent compared with 90 percent for nonresistant TB.

Basics

• Tuberculosis is a bacterial infection that you're most likely to catch if you're in close quarters for a long time with someone suffering from an active infection. Symptoms are highly variable. Some people are affected so mildly, they don't even know they have it, while others experience a constant cough, extreme fatigue, weight loss, fever and cough up blood. Sometimes TB goes into a latent phase where it doesn't make you sick and can't be transmitted.

Resistance

• Drug resistance develops when tuberculosis is not treated properly and fully. For example, a doctor might not order an adequate treatment regimen, or a patient may not continue therapy long enough to wipe out all remaining bacteria. Nearly 8 percent of United States TB cases are resistant to isoniazid, which is the treatment of choice for TB, according to the U.S. Centers for Disease Control and Prevention. Some TB germs, according to the American Lung Association, have developed resistance to seven drugs.

First-line Drugs

• The first-line drugs for treatment of TB include isoniazid and rifampin. Isoniazid is the first option for treating latent cases, and it is very important in treating active ones, as well. It is a bacteria-killing drug that can make a patient less likely to spread TB. Rifampin, too, is a powerful bacteria-fighting medication that can help patients avoid a relapse. Approved by the U.S. Food and Drug Administration is Rifater, which is a single-pill combo of isoniazid, rifampin and pyrazinamide (which is also a first-line treatment). Taking all three reduces the chance of your TB infection becoming drug-resistant.

Second-line

• When a tuberculosis strain has become resistant to first-line treatment agents, the patient must be treated with second-line agents. By definition, these drugs are less attractive options. They don't work as well, they cost more and have worse side effects. Additionally, they have to be taken for much longer periods of time--18 to 24 months--as compared with first-line drugs. A minimum of three second-line medications must be taken at once, and one of them should be injectable.

  Examples of second-line TB medications: ethionamide, ethambutol, aminoglycoside, pyrazinamide and fluoroquinolone.

XDR Tuberculosis

• A new threat become known in 2006 in HIV patients in Africa, with the discovery of tuberculosis strains that were resistant to first-line treatment and to some second-line treatments. Scientists have termed the phenomenon extensively drug-resistant (XDR) tuberculosis. It's now been reported in 46 countries and accounts for 4 percent of U.S. cases. A given strain of XDR tuberculosis may still be vulnerable to certain second-line drug options even though it's resistant to others, so aggressive treatment with second-line options can sometimes be successful. Unfortunately, some strains have proven nearly untreatable, and the infection often results in death. Efforts now are focused on preventing drug-resistant TB and developing new drugs.