PK Study of Anti-TB Drugs

This is a prospective descriptive and pharmacokinetic study will be conducted among newly diagnosed patients registered in the two SMRU TB clinics located on the Thai-Myanmar border. This study aims to recruit (1) 30 adults with HIV co-infection and (2) 30 adults without HIV co-infection in one year. Patients will be given the standard 6 month anti-TB drugs as per WHO guidelines.

The threat of tuberculosis and HIV remains as major public health issues all over the world. Multi-drug resistant tuberculosis (MDR TB) is also a rising public health issue. Currently available standardized TB treatment is 6 months in duration. Previous pharmacokinetic and pharmacodynamic (PK/PD) studies of anti-TB drugs have shown that a number of factors such as HIV status, diabetes, malnutrition, age, sex, race, genetics (e.g. NAT2 polymorphisms), drug- drug interactions and food interactions may cause variation of the PK and/or the treatment outcome. But the findings are not persistent from one study to another, for example Chideya S. et al's study in Botswana showed that lower Cmax of anti-TB drugs frequently occurred in TB/HIV coinfected patients and low Cmax of pyrazinamide was related to poor treatment outcomes. On the other hand Requena-Méndez A. et al's study showed the variation of rifampin Cmax was not related to HIV. Large between-patient variability in PK parameters was recently shown to be strongly associated with TB treatment failures and possibly the emergence of drug resistant TB.

The primary objective of this study aims to describe the plasma drug levels of the first-line anti- tuberculosis drugs in two different pulmonary TB patient groups: (1) adults with HIV co-infection and (2) adults without HIV co-infection. The secondary objectives are to investigate the clinical, microbiological and immunological outcomes of the study participants in relation to the plasma drug level and to conduct full genome sequencing and spoligotyping of MTB strains.

Plasma drug levels from venous blood will be measured densely 13 times per day at two occasions: after the first dose on Day 1 and 6 weeks after treatment. Thereafter plasma drug levels will be measured at six hours post-dose on months 2, 3, 4, 5 and 6.

Clinical, microbiological and immunological parameters such as liver and renal function, CRP and LTA4G and sputum examination (smear microscopy, RNA PCR, culture) to monitor clinical progress will also be measured.

The analysis on the plasma drug level in relation to the clinical and microbiological outcomes will be carried out in order to describe the PK/PD of anti-TB drugs and clinical, microbiogical and immunological outcomes in consideration of any possible factors that would influence the relationship between them.