The impact of the introduction of an enantiomer of an already marketed racemic pharmaceutical product on drug utilization and market share in the South African pharmaceutical market

摘要

BACKGROUND:udStereochemistry is often used in the development of drugs. Enantiomers of a chiral drug are two non-superimposable mirror images of the molecule and a racemic mixture consists of equal quantities of both enantiomers. This study looks at the phenomenon of “chiral switching” where a molecule previously developed and marketed by an innovator company as a racemate medicine is later developed and launched as a single enantiomer. Drug utilization and market share data of three molecules that underwent chiral switching were investigated retrospectively to determine the clinical and economic impact of these occurrences in the private South African pharmaceutical market.udMETHOD:udUnit sales and rand sales data of the racemate (and its generics) and the single enantiomer of three drug substance pairs, namely omeprazole-esomeprazole, citalopram-escitalopram and cetirizine-levocetirizine were gathered a year preceding the launch of the single enantiomer to three years subsequent to the launch of the single enantiomer onto the private market.udDATA ANALYSIS:udDescriptive statistical analysis included plotting trend lines of the annual unit and rand sales of both the racemate (and its generics) and the single enantiomer products during the study period, pie charts illustrating the year on year differences in market share (in both unit sales and rand value of sales) as well as box and whisker plots of the racemate and its generics plotted for the year before the single enantiomer was launched, the year after its launch, two years after launch and three years after launch.udThe probability of the enantiomer being prescribed/ sold instead of the racemate at different time points was also calculated to determine whether the drug utilization of the single enantiomer increased or decreased from introduction until three years subsequent to its launch.udCONCLUSION:udResults were consistent with global literature indicating that “chiral switching’ is a successful strategy employed by innovator companies to extend their market share. Drug utilization of the single enantiomer generally showed an upward trend following its launch indicating that there is a perceived belief of enhanced clinical outcomes for the patient. There are, however, many other influencing factors such as pricing strategies, prescription status, marketing efforts to physicians and/or consumers and patent challenges specific to each market that make it difficult to draw a general conclusion from the case studies.