Pharmacogenomics in Healthcare
The range of applications of genomics in healthcare is vast. One area of application that has attracted considerable attention is the use of genomic information to tailor treatments for individual patients; an activity that extends from the drug discovery process to the prescribing of drugs for patients. The term pharmacogenomics, instead of the older term pharmacogenetics, recognises the availability of more powerful molecular technologies to interrogate multiple genes instead of single genes. Both terms can still be used interchangeably.
This article from "The Pharmacist" journal introduces the science of pharmacogenetics and its implications for pharmacy practice, illustrated with examples from oncology and other areas.
Use this article from 'The Pharmacist' to provide an introduction to the science of pharmacogenetics and its implications for pharmacy practice.
Pharmacogenomic information is increasingly used to inform the drug-discovery process and is already used in clinical practice in a variety of areas, and is relevant to anyone interested in the prescription of or use of drugs.
No drug is effective for everyone, and in a few patients, usually safe drugs can produce serious adverse effects.
For most drugs there is a clear dose-effect relationship and dosing involves a trade-off between beneficial and adverse effects.
Pharmacogenetic research is starting to provide the basis for predicting individual response to an increasing range of drugs:
Endocrine therapy, with drugs such as Tamoxifen, is often effective in breast cancer patients. Pharmacogenetic testing helps to identify the more likely responders and helps ensure that treatment of likely non-responders with alternative agents is not unnecessarily delayed.
Codeine acts as an effective painkiller after conversion to morphine, which is in turn detoxified and excreted. If too much morphine is produced or if its excretion is impaired, normal doses of codeine may become toxic. Individual genetic differences, as well as concomitantly prescribed drugs, may affect these metabolic pathways with clinical implications.
Our bodies produce metabolic enzymes that detoxify and process most drugs. These enzymes may be impaired by genetic mutations or interactions with other drugs or foods, and lead to serious clinical effects.
Cancer cells show high genetic instability. In fact, most cancer patients die following genetic changes in tumours that lead to drug resistance. Pharmacogenetics contributes to the development of better treatment strategies. In some cancers, such as chronic myelogenous leukaemia, positive treatment effects can be dramatic.
This factsheet describes how genomic insights have lead to improved treatments for many types of cancer.
A few HIV-AIDS patients given Abacavir, an antiretroviral drug, develop a potentially lethal hypersensitivity reaction. Pharmacogenetic testing now allows us to identify many of them.
Tuberculosis is still one of the major killers. A recent threat is the emergence of extensively drug resistant (XDR) strains. Rapid aggressive therapy is required to cure the patient and also to prevent the spread of the disease. Testing allows rapid identification of XDR microorganisms.
This factsheet describes the principles, progress, and challenges of gene therapy.
Sometimes it is not easy to identify infective microorganisms. For example with Chlamydia infection, carriers may not know they are infected. Molecular testing allows rapid and reliable identification of the microorganism and use of effective antibiotic therapy.
Many new drugs are only modestly effective but enormously expensive; so much so that the National Institute of Clinical Excellence judge them to be not cost-effective for the National Health Service. Yet sometimes a few patients derive considerable benefit from such drugs. As pharmacogenetic testing becomes more accurate, targeting the likely responders would make prescribing more affordable.
How will pharmacogenetics impact on pharmacy practice?
The Centre held a meeting with pharmacy stakeholders in collaboration with the Royal Pharmaceutical Society of Great Britain to discover pharmacists’ views of pharmacogenetics, to determine the role that pharmacists felt they could play in offering a pharmacogenetics service to the public and to highlight the educational needs of pharmacists of this topic. Conclusions and recommendations are in our report
Use this report to understand the role that pharmacists feel they could play in offering a pharmacogenetics service to the public and to highlight the educational needs of pharmacists of this topic.
The participants identified a role for the pharmacist in expanded services. Examples included the provision of testing for chlamydia, and advising about potential interactions between genetic variation and over the counter drugs, such as the example in the box.
Potential interactions between over-the-counter drugs and an inherited condition
- Miss Browne, aged 27, asks her pharmacist for some advice.
- Her 18 year old cousin, previously perfectly healthy, recently died while running the London marathon; post-mortem genotyping identified a mutation known to cause the Long QT syndrome.
- Miss Browne asks whether she should be tested. She is particularly worried as she fainted at the gym recently.
- She asks whether any medicines or herbs should be avoided.
- She is currently using an antihistamine for hay-fever and fluoconazole for thrush, both bought over-the-counter and various ‘health’ herbs. She is on prescribed diuretics for Premenstrual Syndrome.
The participants also identified where pharmacogenetics may impact on the services provided by pharmacy practitioners, as summarised in the figure.
The nature of the tasks required and the skills that pharmacists would need to fulfil an extended role were identified. The skills identified were those which pharmacists had and used on a regular basis, so in developing a pharmacogenetics service, it was suggested that pharmacists would need new knowledge, but not new skills.