Febuxostat is contraindicated with concomitant use of theophylline and chemotherapeutic agents , namely azathioprine and 6 - mercaptopurine .
Use could increase blood plasma concentrations of these drugs .
Febuxostat is contraindicated with concomitant use of theophylline and chemotherapeutic agents , namely azathioprine and 6 - mercaptopurine , because it could increase blood plasma concentrations of these drugs .