Tuberculosis and HIV disease

November 2004     View PDF     En español

Drug resistance

Over the past decade there has been an increase in the appearance of strains of TB that are resistant to two or more anti-TB drugs. These strains are called multi-drug resistant TB, or MDR-TB. Resistance can occur if someone does not take a full course of treatment or if an extra drug is merely added to an already failing anti-TB therapy regimen. Once someone has developed drug-resistant TB they can transmit that TB to others, leaving those newly infected with fewer treatment options. Drug-resistant TB is more difficult to treat and more likely to cause death as a consequence.

In 1997, over 7% of TB strains were resistant to at least isoniazid, and 1.3% were resistant to at least isoniazid and rifampin. People with HIV are six times more likely to have MDR-TB than HIV-negative people. MDR-TB is three times more likely than drug-sensitive TB to cause active disease in HIV-positive people.

The box below shows treatment plans for TB resistant to either rifampin or isoniazid. If there is resistance to both, at least three new potent drugs should be used. Treatment may take up to 24 months, and sometimes seven or more drugs are needed.

Treating MDR-TB usually includes the use of an aminoglycoside [amikacin (Amikin), capreomycin (Capastat), etc.] and a fluoroquinolone [ciprofloxacin (Cipro), ofloxacin (Zagam), etc.]. Aminoglycosides (streptomycin, kanamycin, and amikacin should not be used during pregnancy because it can harm the unborn baby. Other drugs include rifabutin, cycloserine (Seromycin), ethionamide (Trecator-SC), clofazamine (Lamprene), and para-aminosalicylic acid. After treatment has finished, patients are encouraged to see their doctor every four months for two years to check for TB recurrence.

In more severe cases of TB, surgery may be used to remove infected tissue. Steroids are sometimes used to reduce inflammation and control tissue damage, as is the case when TB affects the brain.