RT Journal A1 McKINSEY DS, DURFEE D, KURTIN PJ T1 MEgaloblastic pancytopenia associated with dapsone and trimethoprim treatment of pneumocystis carinii pneumonia in the acquired immunodeficiency syndrome JF Archives of Internal Medicine JO Archives of Internal Medicine YR 1989 FD April 1 VO 149 IS 4 SP 965 OP 965 DO 10.1001/archinte.1989.00390040157038 UL http://dx.doi.org/10.1001/archinte.1989.00390040157038 AB To the Editor.—Trimethoprim has been prescribed frequently in combination with sulfamethoxazole or dapsone for treatment of Pneumocystis carinii pneumonia in patients with the acquired immunodeficiency syndrome (AIDS).1,2 Use of these medications is associated with leukopenia in a substantial proportion of cases.3 Some authors have suggested that supplemental folinic acid (leucovorin) should be administered to prevent bone marrow suppression in patients with AIDS treated with sulfonamides.4 This issue has been controversial, however, and no clear consensus has emerged. We report a case in which treatment of P carinii pneumonia with trimethoprim and dapsone in a patient with AIDS and subclinical vitamin B12 deficiency resulted in megaloblastic pancytopenia. This complication probably would have been prevented by use of supplemental folinic acid.Report of a Case.—A 36-year-old man under our care for AIDS and P carinii pneumonia was treated with orally administered trimethoprim and dapsone. No other