Pancytopenia caused by allopurinol and azathioprine interaction in a heart transplant patient: a case report.

Azathioprine and allopurinol can potentially cause profound cytopenias due to the increased production of the active metabolites of azathioprine. Given the association between gout and solid organ transplantation, recognition of the risks of medication interaction as well as communication amongst health care providers and between providers and their patients is paramount.