Discordance Between Availability of Pharmacogenetics Studies and Pharmacogenetics-Based Prescribing Information for the Top 200 Drugs

BACKGROUND: Despite growing numbers of pharmacogenetics studies, little pharmacogenetics-based prescribing information is available to practitioners. It is possible that the lack of prescribing data for commonly used drugs is due to a paucity of evidence-based pharmacogenetics literature for these agents. OBJECTIVE: To investigate the relationship between pharmacogenetics prescribing data in drug package inserts (PIs) and pharmacogenetics research literature for agents represented in the top 200 prescribed drugs for 2003. METHODS: A PubMed search (to August 7, 2004) was performed to identify pharmacogenetics studies relevant to the top 200 drugs. These data were compared with PIs for drugs in the top 200 list that contained pharmacogenetics prescribing information. RESULTS: Pharmacogenetics data in the literature were available for 71.3% of the top 200 drugs. The gene involved coded for a drug-metabolizing enzyme in 34.5% of the literature sampled. The remaining 65.5% of the pharmacogenetics studies contained information largely related to genetic variability in target proteins and drug transporters. Three drugs with PIs containing pharmacogenetics prescribing information deemed to be useful to guide therapy were in the top 200 list (celecoxib, fluoxetine, pantoprazole). There was no consensus on the strength of association between genetic variability and drug response for these agents. CONCLUSIONS: The lack of specific pharmacogenetics-based prescribing information in PIs for commonly used drugs does not seem to be related to a paucity of pharmacogenetics data in the research literature. Rather, other factors including, but not limited to, the uncertain clinical relevance of genetic associations may make practical prescribing recommendations difficult.