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Potentially Unintended Discontinuation of Long-term Medication Use After Elective Surgical Procedures
Chaim M. Bell, MD, PhD;
Jana Bajcar, BScPhm, MScPhm, EdD;
Arlene S. Bierman, MD, MS;
Ping Li, PhD;
Muhammad M. Mamdani, PharmD, MA, MPH;
David R. Urbach, MD, MSc
Arch Intern Med. 2006;166:2525-2531.
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  -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 -blocker ophthalmic drops were not at increased risk.
Author Affiliations: Departments of Medicine (Drs Bell and Bierman), Health Policy Management and Evaluation (Drs Bell, Bierman, and Urbach), Family and Community Medicine (Dr Bajcar), and Surgery (Dr Urbach), and Faculties of Pharmacy (Drs Bajcar and Mamdani) and Nursing (Dr Bierman), University of Toronto; Institute for Clinical Evaluative Sciences (Drs Bell, Bierman, Li, Mamdani, and Urbach); Department of Medicine, St Michael's Hospital (Drs Bell and Bierman); Cancer Care Ontario and Department of Surgery, University Health Network (Dr Urbach); Toronto, Ontario.
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