Drug Therapy Gets Personal with Genetic Profiling

Pharmacogenetics Holds Great Promise for Improving Prescribing Practices and Avoiding Adverse Effects

Dana Bartlett, MSN, RN

Disclosures

Am Nurs Journal. 2011;6(5):23-28. 

In This Article

Not Just an Abstract Science

Pharmacogenetics may sound abstract and theoretical, but the science is becoming well established. Clearly, genetics and drug performance are inseparable. For a small minority of drugs, pharmacogenetics already influences prescribing practices. (See Examples of personalized drug therapy.)

The Food and Drug Administration (FDA) now requires drug manufacturers to include information about a drug's effects on the CYP450 enzyme system and how genetic variants of this system influence the drug's metabolism and adverse effects. Currently, labeling for more than 50 drugs includes pharmacogenetic information. The FDA also has issued guidelines for using genetic polymorphism information in clinical trials of drugs.

Genetically Based Dosing Algorithms

Evidence from randomized controlled trials suggests that dosing algorithms based on genetic information can be valuable and may improve patient outcomes. Researchers predict drug prescribing will soon be based partly on genetic profiling. Given that differences in an SNP may produce a tenfold variation in blood drug concentrations, pharmacogenetics appears to have great potential to improve prescribing practices and help avoid adverse effects.

Yet, although we know that genes and pharmacology are inextricably linked, we don't know how, when, and in what ways. More importantly, it's not yet possible to use pharmacogenetic knowledge in a practical way. The FDA doesn't require genetic testing for patients starting warfarin therapy. Pharmacogenetic algorithms and pharmacogenetic testing aren't used in everyday clinical practice. And no randomized trials have proven unequivocally that this dosing approach has value. In a May 2009 memo, the Centers for Medicare & Medicaid Services stated it won't pay for genetic testing to determine warfarin dosing for Medicare recipients because no evidence shows that pharmacogenomic testing to predict warfarin response improves health outcomes. (See Pharmacogenetic testing: Not ready for prime time.)

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