Tuberculosis and HIV disease

November 2004     View PDF     En español

Preventing active disease

People with TB infection can take drugs to help prevent them from developing active disease. This is called TB prevention or prophylaxis. People living with HIV are encouraged to consider TB preventive therapy if TB skin testing has come back positive, if there has been contact with someone with active TB disease or if it’s determined that a prior episode of TB disease was not treated properly.

It’s important that a doctor make sure that a person does not have active TB before starting TB preventive therapy. This is because preventive therapy is less intensive than TB treatment for active disease and if active disease is present but not yet expressing itself fully, resistance to TB drugs could rapidly develop due to sub-optimal treatment. Isoniazid is the most common TB preventive therapy. It has few side effects and is cheap. It is usually taken daily or twice a week for nine months.

Studies also show that a two-month course of rifampin (600mg once a day) plus pyrazinamide (20mg/kg once a day) prevents active disease as well as 12 months of isoniazid. There is no difference in the amount of side effects between the two. The two-month course is also useful if the TB is thought to be resistant to isoniazid.

Preventive TB therapy is not usually given to people thought to be anergic. However, if someone who is anergic is determined to be at high risk for TB infection, they may be given TB preventive therapy. Pregnant women with TB infection are advised to start isoniazid preventive therapy right away, even in the first trimester. Children who need preventive therapy should take isoniazid for twelve months.

If the TB strain is resistant to both isoniazid and rifampin, prophylaxis preventive therapy may be difficult. In this case, options include pyrazinamide plus one of ethambutol, ofloxacin or ciprofloxacin daily for six months. Preventive therapy using three drugs has been tested but is not often used due to side effects.