Pharmacogenetics: Pharmacists should own it, not fear it

Just in the past 18 months the promise of the human genome revolution has become a lot more promising.

Owing to technological breakthroughs for genotyping, as well as the groundbreaking haplotype map (HapMap), which catalogues human genetic variations, the costs of a study to link genetic variation with a particular condition has dropped almost miraculously from about $10 billion to under $1 million since 2002, according to scientists at the National Human Genome Research Institute.

In 2007 completed studies began to roll in at a much more rapid pace, said Francis Collins, M.D., Ph.D., head of the institute: "It is in fact astounding that we can be here in 2008 and actually talk about having done this now for dozens of diseases." And the rate of discovery is likely to speed up.

Collins said because any newly identified genes and their protein products are possible drug development targets, "pharmaceutical companies are wrestling a little bit with what to do with this experience of drinking from a fire hydrant."

What does this mean for the working pharmacist? Drug Topics recently talked to Howard McLeod, Pharm.D., head of the editorial board for Pharmacogenomics: Applications to Patient Care, a publication of the American College of Clinical Pharmacology.

Another variable

"To me the essence of good clinical pharmacy is trying to understand why there is variability between people. And pharmacists are very good at looking at the impact of a drug interaction or the impact for kidney or liver function, the impact of age or in some cases gender," said McLeod.

Genetics will be another variable to add to that mix, he explained: "And I would like pharmacists to think of any variable that will help them understand their patients as one that they should own."

Pharmacists should understand how genetic information is generated and how it can be applied, McLeod believes. "But they should not be any more scared about a factor like genetics than they are about kidney function or a drug-drug interaction," said McLeod, who is director of the University of North Carolina Institute of Pharmacogenomics and Individualized Therapy.

What pharmacists need to know

It is imperative, said McLeod, that any pharmacist who is interacting with patients make it a priority to get continuing education in pharmacogenetics, whether it is online or at a national or local meeting.

Pharmacists don't have to become molecular biologists, he clarified, but they need to understand basic terms such as "genotype" and "allele." After that point, he said, "Just like you pay attention to what new drug interactions have been identified, you may also pay attention to what new gene-drug interactions have been identified."

Rapid introduction

McLeod agrees that the growth in pharmacogenetics is likely to be rapid: "Every few months or so there will be a new example that one has to evaluate and decide whether it is right for their practice. And when it is, start applying it."

He noted that the better medical centers are already using genetics to guide some therapy, including warfarin and tamoxifen therapy, and that large national labs are offering pharmacogenetic testing.

"They are doing direct-to-consumer marketing, they are doing direct-to-physician marketing, and they are serving pharmacists. So there is no one in the United States who does not have access to pharmacogenetic tests," he said.

"This will not be a case where every drug needs a gene test. But for those drugs with narrow therapeutic index, or where some especially significant adverse events occur, there may well be a therapeutic test that will help make this drug a lot more manageable," said McLeod.