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.

Investigators performed a population-based, cohort study using administrative records from Ontario, Canada, between April 1, 1997 and September 30, 2002.  They 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 one or more years.  Those who had an overnight hospitalization for selected elective surgical procedures were compared with two 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 six months.

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 ration (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]).

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.