Effect of generics on price and consumption of ciprofloxacin in primary healthcare: the relationship to increasing resistance.

Background: The introduction of generic versions of drugs has often resulted in an increase in the consumption of the agents involved. In December 2001, generic ciprofloxacin was marketed in Denmark. Our objective was to evaluate, in a community setting, the effect of price on consumption of ciprofloxacin and on ciprofloxacin resistance in Escherichia coli urine isolates.
Methods: We conducted a retrospective ecological study collecting monthly national data on the number of marketed versions and primary healthcare (PHC) sales of ciprofloxacin during January 1995-December 2005. Data were compared with a median price per defined daily dose (DDD) of ciprofloxacin during September 1999-December 2005. Yearly PHC consumption data from seven Danish counties were compared with the antimicrobial resistance profiles of PHC E. coli urine isolates.
Results: During 2002, the number of marketed versions increased from 3 to 10, and the median price per DDD decreased by 53%. From 2002 to 2005, the total consumption of oral ciprofloxacin in PHC increased significantly from 0.13 DDD/1000 inhabitant-days to 0.33 DDD/1000 inhabitant-days. During the same period, the frequency of ciprofloxacin resistance increased by 200%. A statistically significant correlation was found between the consumption of ciprofloxacin and the ciprofloxacin resistance rate in E. coli urine isolates, independent of the introduction of generic ciprofloxacin.
Conclusions: After the introduction of generic ciprofloxacin, a significant increase in the total consumption of oral ciprofloxacin in PHC was observed in Denmark. The increase in consumption was significantly correlated with ciprofloxacin resistance in E. coli obtained from urine isolates.