title: Potentially unintended discontinuation of long-term medication use after elective surgical procedures.
abstract: BACKGROUND
  Transitions between health care settings represent vulnerable periods for medical error. Discontinuation of long-term medication use may occur during discharge from the hospital to the community.
  
  
  METHODS
  We performed a population-based, cohort study using administrative records from Ontario, Canada, between April 1, 1997, and September 30, 2002. We studied all residents 66 years and older with continuous use of warfarin, 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins), or beta-blocker ophthalmic drops for 1 or more years. Those who had an overnight hospitalization for selected elective surgical procedures were compared with 2 control groups: one that had an ambulatory procedure and one that had no procedures. All groups were assessed for the outcome of failure to renew the prescription within 6 months.
  
  
  RESULTS
  Rates of drug treatment discontinuation after overnight hospitalizations, after ambulatory procedures, and after no procedures were 11.4%, 7.5%, and 4.8%, respectively, in the warfarin group; 4.0%, 3.9%, and 3.9%, respectively, in the statin group; and 8.4%, 8.9%, and 7.9%, respectively, in the ophthalmic drops group. The adjusted odds ratio (OR) was 2.6 (95% confidence interval [CI], 2.0-3.4) for discontinuation of warfarin therapy after overnight hospitalizations and 1.6 (95% CI, 1.4-1.7) after ambulatory procedures. In contrast, there was no increased risk of discontinuing treatment with either statins (OR for overnight hospitalization, 1.0 [95% CI, 0.9-1.2]; OR for ambulatory procedure, 1.0 [95% CI 1.0-1.1]) or ophthalmic drops (OR for overnight hospitalization, 1.0 [95% CI, 0.8-1.5]; OR for ambulatory procedure, 1.1 [95% CI, 1.0-1.2]).
  
  
  CONCLUSIONS
  Patients prescribed long-term therapy with warfarin were at risk for potentially unintended medication discontinuation after elective procedures. Patients prescribed statins or beta-blocker ophthalmic drops were not at increased risk.
authors.affiliation: Department of Medicine, University of Toronto, Toronto, Ontario, Canada. bellc@smh.toronto.on.ca
authors.forename: Chaim M
authors.initials: CM
authors.lastname: Bell
authors.forename: Jana
authors.initials: J
authors.lastname: Bajcar
authors.forename: Arlene S
authors.initials: AS
authors.lastname: Bierman
authors.forename: Ping
authors.initials: P
authors.lastname: Li
authors.forename: Muhammad M
authors.initials: MM
authors.lastname: Mamdani
authors.forename: David R
authors.initials: DR
authors.lastname: Urbach
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000556:Ambulatory Surgical Procedures; D000925:Anticoagulants / Q000008:administration & dosage*; D017558:Elective Surgical Procedures; D005260:Female; D006801:Humans; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000008:administration & dosage*; D008297:Male; D008508:Medication Errors / Q000706:statistics & numerical data*; D009864:Ontario; D009883:Ophthalmic Solutions / Q000008:administration & dosage*; D010352:Patient Dropouts / Q000706:statistics & numerical data*; D011184:Postoperative Period; D014859:Warfarin / Q000008:administration & dosage*
chemical_list: D000925:Anticoagulants; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D009883:Ophthalmic Solutions; D014859:Warfarin