Sulfamethoxazole/trimethoprim (Bactrim DS) 
Hematologic: Agranulocytosis, aplastic anemia, thrombocytopenia, leukopenia, neutropenia, hemolytic anemia, megaloblastic anemia, hypoprothrombinemia, methemoglobinemia, eosinophilia, thrombotic thrombocytopenic purpura, idiopathic thrombocytopenic purpura.
Chronic: Use of Bactrim at high doses and/or for extended periods of time may cause bone marrow depression manifested as thrombocytopenia, leukopenia and/or megaloblastic anemia. If signs of bone marrow depression occur, the patient should be given leucovorin 5 to 15 mg daily until normal hematopoiesis is restored.
Thrombocytopenia: Bactrim-induced thrombocytopenia may be an immune-mediated disorder. Severe cases of thrombocytopenia that are fatal or life-threatening have been reported. Thrombocytopenia usually resolves within a week upon discontinuation of Bactrim.
Geriatric Use: In those concurrently receiving certain diuretics, primarily thiazides, an increased incidence of thrombocytopenia with purpura has been reported.
Bactrim is contraindicated in patients with a history of drug-induced immune thrombocytopenia with the use of trimethoprim and/or sulfonamides.