1,5-Dihydro-4H-pyrazolo[3,4-d]pyrimidin-4-one (as per EP & USP) ; Allopur; Caplenal; Cellidrin; Allopurinol - API (IP); 4-Hydroxypyrazolo(3,4-d)pyrimidine; 4-Hydroxypyrazolo[3,4-d]pyrimidine; 4-Hydroxypyrazolo[3,4-d]pyrimidine; 4-Oxopyrazolo[3,4-d]pyrimidine; Adenock; Allopur; Caplel; Cellidrin; 4H-Pyrazolo[3,4-d]pyrimidin-4-one, 1,5-dihydro; 1,5-Dihydro-4H-pyrazolo[3,4-d]pyrimidin-4-one; 1H-Pyrazolo[3,4-d]pyrimidin-4-ol (USP);