Adverse events associated with prescription drug cost-sharing among poor and elderly persons

Context Rising costs of medications and inequities in access have sparked c alls for drug policy reform in the United States and Canada. Control of dru g expenditures by prescription cost-sharing for elderly persons and poor pe rsons is a contentious issue because little is known about the health impac t in these subgroups. Objectives To determine (1) the impact of introducing prescription drug cos t-sharing on use of essential and less essential drugs among elderly person s and welfare recipients and (2) rates of emergency department (ED) visits and serious adverse events associated with reductions in drug use before an d after policy implementation. Design and Setting Interrupted time-series analysis of data from 32 months before and 17 months after introduction of a prescription coinsurance and d eductible cost-sharing policy in Quebec in 1996, Separate 10-month prepolic y control and post-policy cohort studies were conducted to estimate the imp act of the drug reform on adverse events. Participants A random sample of 93 950 elderly persons and 55 333 adult wel fare medication recipients. Main Outcome Measures Mean daily number of essential and less essential dru gs used per month, ED visits, and serious adverse events (hospitalization, nursing home admission, and mortality) before and after policy introduction . Results After cost-sharing was introduced, use of essential drugs decreased by 9.12% (95% confidence interval [CI], 8.7%-9.6%) in elderly persons and by 14.42% (95% CI, 13.3%-15.6%) in welfare recipients; use of less essentia l drugs decreased by 15.14% (95% CI, 14.4%-15.9%) and 22.39% (95% CI, 20.9% -23.9%), respectively. The rate (per 10000 person-months) of serious advers e events associated with reductions in use of essential drugs increased fro m 5.8 in the prepolicy control cohort to 12.6 in the postpolicy cohort in e lderly persons (a net increase of 6.8 [95% CI, 5.6-8.0]) and from 14.7 to 2 7.6 in welfare recipients (a net increase of 12.9 [95% CI, 10.2-15.5]). Eme rgency department visit rates related to reductions in the use of essential drugs also increased by 14.2 (95% CI, 8.5-19.9) per 10000 person-months in elderly persons (prepolicy control cohort, 32.9; postpolicy cohort, 47.1) and by 54.2 (95% CI, 33.5-74.8) among welfare recipients (prepolicy control cohort, 69.6; postpolicy cohort, 123.8). These increases were primarily du e to an increase in the proportion of recipients who reduced their use of e ssential drugs. Reductions in the use of less essential drugs were not asso ciated with an increase in risk of adverse events or ED visits. Conclusions In our study, increased cost-sharing for prescription drugs in elderly persons and welfare recipients was followed by reductions in use of essential drugs and a higher rate of serious adverse events and ED visits associated with these reductions.