Which of the following describes the action of allopurinol

URIC ACID SYNTHESIS INHIBITORS Allopurinol:- Mech of action:- Allopurinol is a sho-acting (t 1/2 2 hrs) competitive inhibitor of xanthine oxidase, but its major metabolite alloxanthine (oxypurine) is a long-acting (t 1/2 24 hrs) and noncompetitive inhibitor--primarily responsible for uric acid synthesis inhibition in vivo. At high concentrations, allopurinol also becomes noncompetitive inhibitor. During allopurinol administration, plasma concen tration of uric acid is reduced and that of hypoxanthine and xanthine is somewhat increased. Because of raised levels of xanthine and hypoxanthine, some feedback inhibition of de novo purine synthesis and reutilization of metabolically derived purine also occurs. Ref:- kd tripathi; pg num:-216