Impact of safety warnings on drug utilization: marketplace life span of cisapride and troglitazone.
STUDY OBJECTIVE
To evaluate the impact of safety alerts on the volume of cisapride and troglitazone usage.


DESIGN
Retrospective database analysis.


SETTING
University research center.


MATERIAL
Idaho Medicaid claims data from January 1994--July 2000.


MEASUREMENTS AND MAIN RESULTS
Monthly counts of total and new prescriptions filled for cisapride and troglitazone were analyzed graphically over time as a function of all prescriptions. New prescriptions were defined as those filled by patients who had not received the drug within the previous year. A binomial comparison of the 5 months before and after each safety alert was conducted by Poisson distribution. Overall and new cisapride usage increased after the first alert, which occurred in February 1995 (p<0.05). After the second alert, in September 1995, growth in new prescriptions ended but total prescriptions continued to grow (p<0.05). After the third alert, in June 1998, growth in total use ended and the number of new prescriptions declined (p<0.05). The final two alerts (June 1999 and January 2000) were met with significant declines (p<0.05 for both). Troglitazone was the subject of two alerts in October and December 1997. After these, overall usage increased (p<0.05), whereas the number o new prescriptions decreased (p<0.05). The third alert, in July 1998, caused no change as total prescription use continued to grow (p<0.05), whereas the number of new prescriptions decreased (p<0.05). A fourth alert, in June 1999, resulted in a decrease of overall usage and new prescriptions (p<0.05 for both).


CONCLUSION
Numerous safety alerts were required for each drug before drug usage declined. The decline in overall use was slower than the decline in new prescriptions, possibly indicating a need for increased assessment of refilled prescriptions after the release of new safety data.