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Published on 1 July 2005

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Pharmacogenomics: the pharmacist’s view

teaser

Tina Penick Brock
RPh MS EdD
Clinical Associate Professor

John M Valgus
PharmD BCOP
Clinical Assistant Professor/Clinical Specialist, Oncology
School of Pharmacy
University of North Carolina at Chapel Hill
University of North Carolina Hospitals
Chapel Hill, NC
USA
E:tbrock@unc.edu

Despite millions of dollars and many years in development and testing, medications often do not work as well as expected and even cause unanticipated effects. One reason for the difference between efficacy in clinical trials and effectiveness in practice is that patients may intentionally or unintentionally fail to take their medications as directed. But even those who demonstrate optimal adherence can experience results that challenge our clinical expectations. When this happens (eg, an adherent patient fails to respond appropriately or develops an unexplained adverse event), the pharmacist reviews the case and the corresponding literature to consider whether allergies, previous adverse reactions or concomitant medications can explain the phenomenon. But could it be that the true explanation lies within the most innate of patient attributes – their genes?

In this article, we will summarise the potential use of pharmacogenomic information by pharmacists. In addition, we will address several challenges to the optimal use of such information. Although we will not be able to delve into the scientific concepts in detail, our goal is to raise awareness of the issues that will likely face individual clinicians, as well as society, as we increasingly apply pharmacogenomics in healthcare.

“In the future, clinicians will routinely perform genetic tests before selecting or recommending a therapy because they will be able to identify poor responders and those at risk for toxicity.” This statement paraphrases a remark made by Dr Frances Collins, noted scientist and Director of the National Institutes of Health (NIH) National Human Genome Research Institute. It suggests how the science of pharmacogenomics will affect the workflow of healthcare. Armed with this new genomic knowledge, decisions about drug therapy can be made more precisely and allow clinicians to determine whether a particular drug will be useful for a particular patient.
 
Indeed, genetic information can be used to understand diseases better, target treatments and predict response to therapy. In clinical practice, pharmacists will find that this new information can be integrated into the established scientific areas of kinetics and dynamics. Numerous polymorphisms are currently known to affect drug response, and there are increasing numbers of examples to demonstrate these applications in pharmacy. As the availability of genetic information becomes more prevalent, we can use these data to ensure fewer cases of drug failure.
 
The role of pharmacogenomics in pharmacy practice
In the healthcare arena, pharmacists play a key role in medication therapy management. They are often the most accessible provider, they have expertise in pharmacology, they use technology for other therapeutic functions and they are already involved in individualised dosing based on pharmacokinetic parameters. So how will pharmacogenomic considerations complement this professional role? Based on the 1990 statement by Hepler and Strand(4)     concerning pharmacy’s mandate for safe and effective drug therapy in 1990, the answer is … perfectly. Furthermore, the concept of pharmaceutical care, as adopted by the International Pharmaceutical Federation (FIP) in 1998, encompasses drug therapy used to optimise outcomes. In this way, pharmacogenomic therapeutics is the natural progression of the concept of pharmaceutical care. The availability of genetic information will improve our ability to use medications safely and effectively for optimal outcomes.
 
The National Coalition for Health Professional Education in Genetics (NCHPEG) is a group comprising leaders from more than 100 diverse health professional organisations, consumer groups, government organisations and genetics professional societies (see Resources). This group has established core competencies in the related field of genetics that are essential for all healthcare professionals. Competency in these areas (shown in Table 1) represents the minimum knowledge, skills and attitudes necessary for all health disciplines (eg, medicine, nursing, pharmacy and social work) to provide patient care that involves awareness of genetic issues and concerns.

[[HPE21_table1_18]]
 
Although all pharmacists will need to show minimal competency, previous discussions have suggested roles for the genomics-enhanced pharmacist as a researcher, educator and clinician.(1) For these roles to be actualised, however, the model for educating pharmacy students and pharmacists must change to allow for the development of professionals in each of these areas. Introducing new concepts into an existing (crowded) curriculum can be exceedingly difficult, but dynamic models suggest ways to integrate this content into current science, practice and ethics courses.(1)
 
The results from the Human Genome Project have been distributed widely, and this aggressive timeline (actually completed ahead of schedule) has challenged the readiness of pharmacy practitioners in using this information optimally. The American College of Clinical Pharmacy recently published a three-module primer entitled Pharmacogenomics: applications to patient care, designed to prepare pharmacists to integrate pharmacogenomic principles into practice. This effort, along with the results of a survey described in a previous paper, suggests that pharmacogenomics is “on the radar screen” of US national pharmacy organisations; however, the introduction of this content into the curricula of many schools and colleges has been slow.(2) Indeed, while there is some agreement about the potential role of pharmacogenomics in drug therapy decisions, there is less concordance about how best to prepare our current and future practitioners.
 
Use of genetic information in decision-making
A great challenge to our profession is to balance the emergence of this area of science and its integration into our practices. If we assume that genetics may soon drive selection in even 5% of drug therapy decisions, then identification of genotype will be the rate-limiting step for determining risk for disease, need for treatment, development of dosage regimens, response to treatment and risk for toxicity. This issue was discussed recently in a review by Evans and Relling.(3) In this analysis, the authors describe purely genetic diseases or risks as relatively rare; however, they summarise what is currently known about polymorphisms and suggest examples of how cost-effective and widely available testing might be able to predict poor metabolisers of warfarin, poor responders to codeine, patients at risk of toxicity from 6-mercaptopurine, patients at risk from the gastrointestinal toxicity of irinotecan and poor responders to beta-agonists.
 
Although the availability of genetic information holds many promises for medication management and the potential for economic savings by treating only patients likely to respond appropriately, there are still some challenges. Evans and Relling point out that many times the response to therapy may be related to the interplay between polymorphic variations or may relate to a gene–environment interaction in which the expression of the disease will be related to the extent of environmental exposure. These issues increase the complexity of predicting outcomes based solely on genetics, and suggest that the availability of genetic information will not only fail to solve every problem but may also distract us from the true reasons for therapeutic failure.
The future of pharmacogenomics in pharmacy practice
Genetic testing, recording of data, technological interpretation and use of the information to diagnose and treat diseases are already occurring in academic medical centres throughout the world. One of the biggest obstacles to making this a practice standard has been economics; however, costs are decreasing as new testing products become available and compete for market share. Pharmacogenomic microarrays designed for clinical applications, such as the AmpliChip CYP450 Test, are now being used for in-vitro diagnostics in both the USA and the EU (see Resources).

Still, many of the currently identified genetic variations have little clinical relevance for drug therapy decisions. As suggested earlier, the predictors are likely more complex than single polymorphisms; rather, they may be related to combinations of polymorphisms (ie, haplotypes), or combinations of polymorphisms on different genes. Until more is known about this, clinical decision-making is still required to determine the value, clinical utility and appropriateness for testing in each individual patient.

Finally, the availability of pharmacogenomic information is not without risk to privacy and availability of health services. Recognition of these ethical challenges and training in the appropriate use of information by all clinicians, including pharmacists, is critical for the advancement of care. Indeed, the use of pharmacogenomic information by pharmacists has both tremendous opportunities and significant challenges. Preparing the profession for this potential is a major undertaking, but a necessary one.

There are no conflicts of interest or financial concerns  associated with this article

References

  1. Brock TP, Valgus JM, Smith SR, Summers KM. Pharmacogenomics: implications and considerations for pharmacists. Pharmacogenomics 2003;4:321-30.
  2. Brock TP, Faulkner CM, Williams DM, Smith SR. Continuing education programs for pharmacists in pharmacogenomics. Am J Health-Syst Pharm 2002;59:722-5.
  3. Evans WE, Relling MV. Moving towards individualized medicine with pharmacogenomics. Nature 2004;429:464-8. 
  4. Hepler CD, Strand LM. Opportunities and responsibilities in pharmaceutical care. Am J Hosp Pharm 1990;47:533-43.

Resources
National Coalition for Health Professional Education in Genetics
W:www.nchpeg.org
AmpliChip CYP450 Test
W:www.roche-diagnostics.com/products_services/amplichip_cyp450.html



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