title: Prescriptions for a toxic combination: use of methotrexate plus trimethoprim-sulfamethoxazole in the United States.
abstract: OBJECTIVE
  To determine the frequency of using the potentially toxic combination of methotrexate and trimethoprim-sulfamethoxazole (TMP-SMX) in outpatient practice in the United States.
  
  
  METHODS
  Data from the National Ambulatory Medical Care Survey for 1993-2010 were used to assess the frequency of using methotrexate with TMP-SMX and associated physician specialties and diagnoses.
  
  
  RESULTS
  TMP-SMX was coprescribed in 22,000 methotrexate visits per year (1.0% of methotrexate visits). Pediatricians prescribed the combination most frequently, and the most common diagnosis was acute lymphoblastic leukemia. There was no significant change over time in coprescription of TMP-SMX with methotrexate (P = 0.4).
  
  
  CONCLUSIONS
  Low-dose TMP-SMX with methotrexate chemotherapy appears to be standard for patients with acute lymphoblastic leukemia; however, other uses appear questionable, and clinicians should be cognizant of the risk for fatal interactions, especially when medications are prescribed by multiple providers.
authors.affiliation: From the Departments of Dermatology, Pediatrics, Pathology, and Public Health Sciences, Center for Dermatology Research, Wake Forest School of Medicine, Winston-Salem, North Carolina.
authors.forename: Scott A
authors.initials: SA
authors.lastname: Davis
authors.affiliation: From the Departments of Dermatology, Pediatrics, Pathology, and Public Health Sciences, Center for Dermatology Research, Wake Forest School of Medicine, Winston-Salem, North Carolina.
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Krowchuk
authors.affiliation: From the Departments of Dermatology, Pediatrics, Pathology, and Public Health Sciences, Center for Dermatology Research, Wake Forest School of Medicine, Winston-Salem, North Carolina.
authors.forename: Steven R
authors.initials: SR
authors.lastname: Feldman
mesh_terms: D000328:Adult; D000368:Aged; D000553:Ambulatory Care / Q000706:statistics & numerical data; D000890:Anti-Infective Agents / Q000008:administration & dosage / Q000009:adverse effects*; D002648:Child; D002675:Child, Preschool; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D016903:Drug Monitoring; D004359:Drug Therapy, Combination; D005260:Female; D019538:Health Care Surveys; D006801:Humans; D007166:Immunosuppressive Agents / Q000008:administration & dosage / Q000009:adverse effects*; D007223:Infant; D007231:Infant, Newborn; D007945:Leukemia, Lymphoid / Q000188:drug therapy; D008297:Male; D008727:Methotrexate / Q000008:administration & dosage / Q000009:adverse effects*; D008875:Middle Aged; D010198:Pancytopenia / Q000139:chemically induced; D010818:Practice Patterns, Physicians' / Q000592:standards / Q000706:statistics & numerical data*; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000188:drug therapy*; D055656:Prescriptions / Q000706:statistics & numerical data*; D018570:Risk Assessment; D012307:Risk Factors; D015662:Trimethoprim, Sulfamethoxazole Drug Combination / Q000008:administration & dosage / Q000009:adverse effects*; D014481:United States
chemical_list: D000890:Anti-Infective Agents; D007166:Immunosuppressive Agents; D015662:Trimethoprim, Sulfamethoxazole Drug Combination; D008727:Methotrexate