Low TB drugs is a risk for PLWA

By Henry Neondo

Low pyrazinamide concentrations in people coinfected with TB and HIV quadrupled the risk of clinical progression, researchers at the 4th International Aids Society conference on HIV Pathogenesis, Treatment, and Prevention taking place in Sydney, Australia report.

The findings are disturbing not only because low anti-TB drug levels pose a risk of poor treatment response, but also because they heighten the chance of resistance to these drugs. Health officials estimate that 77% of all TB patients in Botswana also have HIV infection.

Researchers from the US Centers for Disease Control and other sites collected blood samples 1, 2, and 6 hours after patients at Gaborone’s biggest public outpatient clinic took isoniazid, rifampin, ethambutol, and pyrazinamide for the first time from 1997 through 1999.

Then clinicians monitored patients for 18 months and kept records of TB treatment failure or death. No one in the study group took antiretrovirals.In 2006 the investigators thawed frozen blood samples to measure concentrations of the anti-TB drugs.

The analysis involved 227 people, 157 (69%) of whom had HIV infection. The researchers documented high rates of low concentrations compared with published normal ranges.

Among people without HIV coinfection, low anti-TB drug levels did not correlate with poor treatment outcome.

But in people with HIV and a CD4 count below 200 cells/µL, low pyrazinamide upped the risk of poor outcome more than 4 times.The researchers call for “further efforts to explain these pharmacokinetic aberrations and their link to HIV infection status, TB treatment outcomes and TB drug-resistance.”

About 24 percent of the Botswana population (1.2 million people) between ages 15 and 49 carry the virus-one of the world's highest prevalence rates.

The 2006 Report on the Global AIDS Epidemic, issued by the Joint United Nations Programme on HIV/AIDS in May 2006, reported 18,000 deaths from the disease last year.

Deaths of young adults in recent years have left 120,000 orphans, nearly 7 percent of Botswana's population.

AIDS is known as a fatal disease, but the actual cause of death for many victims is tuberculosis (TB), the most frequently occurring opportunistic disease that attacks the weakened immune system of HIV-positive persons.

A study conducted jointly by U.S. Centers for Disease Control and Prevention (CDC) and Botswana researchers has shown that 38 percent of AIDS deaths in Botswana were actually due to TB.