Selective Therapeutic Interchange Practices in Ontario Acute Care Hospitals

Background: Therapeutic interchange is a means of decreasing drug costs within a hospital formulary system. Little is known about the substitutions made by hospitals that use this approach. Objectives: To determine, for Ontario, which agents are used within selected classes of cardiovascular medications and proton pump inhibitors and to determine whether medications available in generic formulations are used. Methods: A questionnaire was sent to pharmacy directors at all 177 acute care hospitals in Ontario, Canada. Results: Among the 166 hospitals that responded to the survey (response rate 94%), 141 (85%) reported therapeutic interchange programs. Of the hospitals reporting such programs, 76 (54%) included therapeutic interchange of cardiovascular medications. Most frequently included were HMG (3-hydroxy-3-methylglutaryl) CoA reductase inhibitors (statins) (63/141 or 45%), followed by angiotensin converting-enzyme inhibitors (47/141 or 33%) and angiotensin II receptor blockers (20/141 or 14%). Atorvastatin, ramipril, and losartan were the most commonly used in their respective classes. Proton pump inhibitors were included in 116 (82%) of the therapeutic interchange programs. Lansoprazole, pantoprazole, and omeprazole were used almost equally. Medications available in generic formulations were never the most commonly substituted in any class. Conclusions: Therapeutic interchange is practised by most hospital formulary systems, and there is considerable variation in the specific agents used. The observed lack of use of medications that are available in generic formulations may extend to the outpatient setting.