title: Effect of drug interactions on outcomes of patients receiving warfarin or theophylline.
abstract: The effect of drug interactions on costs and other outcomes for hospitalized patients receiving warfarin or theophylline was studied. Data were collected from medical records during a one-year period in two community teaching hospitals in Maryland. The data included demographic information, the duration of study-drug therapy, the number of days spent in the intensive care unit, the length of stay (LOS) in the hospital, the number of prothrombin-time tests and serum theophylline assays, and the test results. A multiple-regression procedure was used to compare outcomes of patients who were prescribed specific drugs interacting with warfarin or theophylline with those of patients who were not. Among warfarin-treated patients, there was a significant difference in each outcome measure (LOS, number of laboratory tests, and test results) between those who received an interacting drug and those who did not; mean LOS was 3.14 days longer in patients given an interacting drug. No significant differences in outcome measures were observed between the two groups of theophylline-treated patients. The cost of the increased LOS attributed to the presence of a drug interacting with warfarin was estimated to range from $779 to $1005 per hospitalization. The cost of additional prothrombin-time tests was estimated at $19-$50. Patients who received warfarin and an interacting drug had an increased LOS, required more laboratory tests, and had longer prothrombin times than patients given warfarin alone; these differences probably led to higher costs.
authors.affiliation: Department of Pharmacy Care Administration, College of Pharmacy, University of Georgia, Athens 30602-2354.
authors.forename: C A
authors.initials: CA
authors.lastname: Jankel
authors.forename: J A
authors.initials: JA
authors.lastname: McMillan
authors.forename: B C
authors.initials: BC
authors.lastname: Martin
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019411:Clinical Laboratory Techniques / Q000191:economics; D003365:Costs and Cost Analysis; D004347:Drug Interactions; D005260:Female; D006801:Humans; D007902:Length of Stay / Q000191:economics; D008297:Male; D008875:Middle Aged; D011517:Prothrombin Time; D012044:Regression Analysis; D012306:Risk; D013806:Theophylline / Q000009:adverse effects* / Q000097:blood / Q000627:therapeutic use; D016896:Treatment Outcome; D014859:Warfarin / Q000009:adverse effects* / Q000627:therapeutic use
chemical_list: D014859:Warfarin; D013806:Theophylline