Impact of administrative restrictions on antibiotic use and expenditure in Ontario: time series analysis

OBJECTIVE: In a potential attempt to guide antibiotic prescribing based on current clinical evidence and mitigate the spread of antibiotic resistance, in March 2001 the Ontario Drug Benefit programme restricted reimbursement of two fluoroquinolone antibiotics--ciprofloxacin and ofloxacin--to its beneficiaries. Our objective was to determine the impact of this policy on the volume and cost of antibiotic prescribing. METHOD: Weekly administrative data on antibiotic prescribing volumes and expenditures were analysed between January 1999 and September 2002 to estimate the effect of the policy changes using time series analysis. RESULTS: The policy changes were associated with a statistically significant shift downwards for the fluoroquinolones as a category (1905 fewer prescriptions each week, representing a saving of Can105, 707 a week), driven by a decrease in prescriptions for ciprofloxacin (2084 fewer prescriptions a week, saving Can129, 421 a week). Nitrofurantoin (200 more prescriptions a week, costing an extra Can2082 a week) and trimethoprim-sulphamethoxazole (532 more prescriptions a week, costing an extra Can1473 a week) demonstrated a statistically significant shift upwards. The latter also showed a decrease in trend and nitrofurantoin an increase in trend during the time period. There was no statistically significant change in either the total number of antibiotic prescriptions or expenditures associated with the policy of limiting their use. CONCLUSIONS: Although no direct cause and effect can be shown with these observational data, the results suggest that the change in reimbursement policy to restrict prescribing of fluoroquinolones decreased their use and associated expenditures. These decreases were offset by increases in the use of other antibiotics. The balance of consequent benefit and harm of these shifts in prescribing patterns needs to be examined carefully. Alternative solutions to encourage appropriate use of antibiotics deserve exploration.