Validation of Cycloserine Efficacy in Treatment of Multidrug-Resistant and Extensively Drug-Resistant Tuberculosis in Beijing, China

Cycloserine (Cs) is recommended by the World Health Organization as a second-line drug to treat multidrug-resistant tuberculosis (MDR-TB); however, its efficacy has never been sufficiently evaluated. To gain some insights into the value of cycloserine for MDR-TB treatment, bacteriostatic effect was determined and patient validations were performed prospectively. The activity of Cs against 104 wild-type strains was determined, and serum Cs concentrations were measured for 73 MDR TB patients 2 h after administration. The treatment outcomes for 27 MDR-TB patients who had baseline isolates and were treated with Cs-containing regimens were followed up. The MICs for 90% of the recruited 104 wild-type strains were below 32 μg/ml. Eighteen out of 52 patients had peak serum concentrations ( ) below 20 μg/ml at the dosage of 500 mg daily, while 13 out of 21 patients had peak serum concentrations higher than 35 μg/ml at the dosage of 750 mg daily. The percentage of favorable treatment outcomes among patients with a /MIC ratio of ≥1 was statistically significantly higher than that among the group with a /MIC ratio of