Prolonged thrombocytopenia associated with procainamide in an elderly patient

OBJECTIVE: To report a case of thrombocytopenia associated with the use of extended-release procainamide hydrochloride in a geriatric patient. CASE SUMMARY: A 77-year-old man was admitted to the hospital for four-vessel coronary artery bypass surgery. He subsequently developed new onset atrial fibrillation and was started on extended-release procainamide on hospital day 7. The patient's platelet count on admission was 229 x 10(9)/L. The platelet count began to decrease on hospital day 22 and was 79 x 10(9)/L by day 30 and 13 x 10(9)/L by hospital day 37. The patient exhibited gross hematuria and lower extremity petechiae. There were no signs of splenic sequestration and other hematologic indices were normal. Procainamide was discontinued on hospital day 32. There was full recovery of the platelet count to baseline 33 days after procainamide was discontinued. DISCUSSION: Other possible medical and drug-related causes of thrombocytopenia are reviewed and ruled out. Previous reports of procainamide-associated thrombocytopenia describe an immune-mediated peripheral destruction of platelets with platelet recovery within three to eight days after drug discontinuation. However, the prolonged recovery period and the presence of antiplatelet antibodies suggest an immune-mediated process in the bone marrow of this patient. CONCLUSIONS: Clinicians should be aware of the possible adverse hematologic effects of procainamide in the elderly.