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  • Writer's pictureDr Edin Hamzić

Pharmacogenetics & Pharmacogenomics 101

Updated: Nov 2, 2023

Tool Long To Read? Just Read The Intro!

Before I start explaining what is pharmacogenetics and pharmacogenomics, I will first explain some basic terms like genetics, genomics and the difference between these two because explaining the difference between these two will make it easier to understand what is pharmacogenetics and pharmacogenomics as well as the difference between pharmacogenetics and pharmacogenomics.

Also, I will shortly introduce the terms pharmacology and the two main areas of pharmacology which are pharmacodynamics, and pharmacokinetics, and their relation to pharmacogenetics.

Here is the outline of this blog post:

What is genetics? What is genomics?

So, I will start with genetics and genomics.

Genetics is the scientific discipline that studies genes, genetic variation, and heredity in organisms. It is a rather old science that goes back to the 19th century and Gregor Mendel who is considered as the father of genetics.

Genetics started gaining momentum in the early 20th century after rediscovering Mendel’s laws. So, overall genetics is focused on understanding heredity and throughout history due to the technical limitations was focused mainly on investigating individual genes or at best set of genes.

However, in the last 30 years, there has been rapid development of genetic technologies, especially genome sequencing technologies. This rapid development was intensified after the release of the draft sequence of the human genome in 2001. To illustrate, not so long ago sequencing any genome was considered a super colossal project. Still, today, sequencing the whole human genome costs a few hundred dollars, which one would not be able to imagine 40 years ago.

This rapid development in genetic sequencing technologies gave rise to a new discipline genomics, which is focused on studying whole entirety of organisms’ genomes. It is essential to underline that genomics is not focused only on sequencing, but also on understanding the structure, function, evolution, mapping, and editing of genomes.

Just to briefly explain what we mean by genome. The genome is considered the entirety of the DNA of one individual. DNA is packaged in chromosomes (in humans, 23 pairs of autosomal and one pair of sex chromosomes (XY: male and XX female)). As I mentioned, due to the advancement of genomic technologies, we can get the entire sequence (well almost complete) of DNA bundled in those chromosomes instead of focusing on individual genes.

What is the difference between genetics and genomics?

So, the difference between genetics and genomics is in its core of chronological or historical nature. 100 years ago, we did not know much about the structure of DNA, let alone being able to sequence anything. Geneticists were using model organisms (they still do) and indirect methodologies (for example, family-based studies) to track the inheritance and hereditary nature of specific traits and disorders. But, genomics, due to the technical capabilities that we have today, can sequence the whole genome, measure the expression of genes and many other things, and associate those with phenotypic and disease information we have.

What is pharmacology?

As I mentioned before I jump to pharmacogenetics and pharmacogenomics let me briefly explain what pharmacology is.

Pharmacology is the science that focuses on how drugs are developed, how they work, and how they impact the human body. In essence, pharmacology explores the effects of drugs and medications on the human body, as well as how the body interacts with these drugs and medications.

What is pharmacokinetics? What is pharmacodynamics?

The two main subfields of pharmacology important in pharmacogenetics and pharmacogenomics are pharmacodynamics and pharmacokinetics. These two subfields are actually focused on the pharmacological effect of a drug:

  1. Pharmacodynamics is focused in very simple terms on what drugs and medications do to the body and how they work to treat diseases or produce desired outcomes.

  2. Pharmacokinetics is the other way around. Pharmacokinetics is focused on what the body does to a drug. It involves understanding how a drug is absorbed, distributed, metabolized, and excreted in the body over time. In simpler terms, it's about how the body processes and handles a medication, including how it's absorbed into the bloodstream, distributed to various tissues, broken down, and eventually eliminated.

Figure 2 illustrates the link between pharmacodynamcis, pharmacokinetics and pharmacogenomics

pharmacogenomics pharmacokinetics pharmacodynamics
Figure 2: Definitions of pharmacogenomics, pharmacokinetics and pharmacodynamics

What is pharmacogenetics and pharmacogenomics?

Finally, we can talk about pharmacogenetics and pharmacogenomics.

In my opinion, pharmacogenetics and pharmacogenomics can easily be used as synonyms. Why? The final goal of both of those is the same, which is customizing your medications based on your genetics.

However, if we go into the details there is an actual difference between pharmacogenetics and pharmacogenomics and it is tightly related to the difference between genomics and genetics.

Pharmacogenetics is an older term created when genomics as a field was not yet present, while pharmacogenomics is a term of a more recent origin. Basically, as I already mentioned the difference between these two reflects the difference between genetics and genomics.

What is the difference between pharmacogenetics and pharmacogenomics?

So, now I will give you my definition for both of the terms:

Pharmacogenetics is a scientific field that goes back to the pre-genomic era, and it is focused on understanding the influence of genetic factors on the action of drugs. Pharmacogenetics is focused on studying the linkage between the individual’s genotype information and the individual’s ability to metabolize a foreign compound. In essence, pharmacogenetics is like a genetic guide for medicine. It looks at your DNA to see how your genes affect how your body responds to different medications. This information helps doctors choose the right medicines and doses that work best for you, so you get the most benefit with fewer side effects.

Timeline of pharmacogenetics pharmacogenomics
Figure 2: Timeline presenting the critical characteristics of pharmacogenetics, pharmacogenomics, and pharmaco-omic.

On the other hand, pharmacogenomics leverages genomics technologies that enable one to obtain genome sequence data or genetic information covering the whole genome instead of investigating and focusing on a single gene. Genomic information can originate not only from the host but also from the pathogen. Furthermore, by using genomic information, it means that pharmacogenomics also leverages gene expression data and influences.

Figure 2 (adapted from link) tries to illustrate the key features based on which the two fields developed. In the case of pharmacogenetics, those are reactive observational and family studies that used reverse engineering where specific adverse drug reactions were backtracked. In addition, specific gene-drug interactions were identified and investigated also using approaches like candidate gene approaches and randomized clinical trials. However, with the emergence of genomics, the other methodological approaches were used to investigate gene drug interactions such as genome-wide association studies and population comparative studies that leverage high-throughput genotyping and sequencing technologies. The fast development of genomic technologies open opportunities to investigate response to drugs and medication by not only leverage genomic information, but also consider metabolome, proteome, transcriptome, combine all that wealth information and leverage machine learning. This new field is now called pharmaco-omics.

What are examples of pharmacogenetics?

There are many potential examples of pharmacogenetics gene-drug interactions and I have written a separate blog post HERE presenting an example between gliclazide, a medication used for the treatment of diabetes mellitus, and genetic variant (SNP) rs5219 that is located in the KCNJ11 gene.

Why Should We Care About Pharmacogenomics?

There are multiple reasons why we should care about pharmacogenetics. As we explained, pharmacogenomics testing can tell us how well a drug will work for any individual and if there are any potential side effects of prescribing a given drug. Pharmacogenomic testing enables doctors to select the most suitable drug/medication and dose of the given drug for a given condition for that individual patient.

What is the purpose of pharmacogenetics and pharmacogenomics?

Following what I already wrote testing for a large number of genetic variants (mutations) that can affect how we respond to drugs means that we can have substantial benefits of pharmacogenomic guided prescription of drugs. Figure 3 illustrates impact that pharmacogenomics can have and already has.

impact of pharmacogenomics: predicting drug dose, preventing adverse drug reactions, improving efficay, predicting the activation of pro-drugs, developing target drugs for cancer therpay, enabling drug discovery
Figure 3: Impact of pharmacogenomics. Adapted "Pharmacogenomics: current status and future perspectives" by Munir Pirmohamed (published in Nature Review Genetics)

Who can potentially benefit from pharmacogenetics and pharmacogenomics?

Multiple healthcare stakeholders can benefit from pharmacogenetics testing such as patients, healthcare providers, healthcare systems and hospitals, payers and insurers, pharmaceutical companies, regulatory agencies, and government health departments. I will shortly explain the potential benefits for each in the following paragraphs.

How can patients benefit from pharmacogenetic testing?

Patients are if not the main then one of the main benefactors since pharmacogenetics testing can provide them with personalized treatment plans that are tailored to their genetic profile. Pharmacogenetics can help patients identify which medications and drugs are potentially the most effective, reducing the risk of adverse drug reactions and improving treatment outcomes. This way, pharmacogenetics enables patients to avoid the trial-and-error approach to finding the right medication, potentially saving time and reducing side effects.

To be more concrete the key potential benefits of pharmacogenomics for patients are:

  • Prevention of adverse drug reactions (ADR): Certain drugs in patients with specific genetic variants have been associated with severe adverse drug reactions (ADR). ADRs affect 10-20% of hospital patients and also account for many emergency admissions to hospitals. Some of those ADRs can be avoided by using pharmacogenetic testing prior to prescription of drugs.

  • Improved drug dosing or so-called precision dosings: Another important benefit that patients can have from pharmacogenomics is dosage adjustment. As they are based on pharmacogenomics, they can improve efficacy and minimize side effects of drug treatments, resulting in better clinical outcomes and patient experiences.

How can healthcare providers benefit from pharmacogenetic testing?

The main benefit of pharmacogenomics for physicians and other healthcare providers is that they can make more informed prescribing decisions. Physicians can avoid prescribing medications that may be ineffective or cause harm to specific individuals. All this can improve patient care by reducing the probability of ADRs, improving medication efficacy, and optimizing dosages.

What is the role of pharmacists in pharmacogenetic testing?

Pharmacists can be critical in interpreting and applying the results of pharmacogenetic tests to ensure safe and effective medication management. They can counsel patients about their genetic response to medications and potential drug interactions.

How can healthcare systems and hospitals benefit from pharmacogenetic testing?

The main potential benefit of healthcare systems is a reduction in hospital readmissions and ADR events and this can lead to cost savings and improved patient outcomes. Also, implementing pharmacogenetic testing programs can improve the reputation of healthcare facilities by offering cutting-edge personalized medicine.

How can payers and insurers benefit from pharmacogenetic testing?

The main value of pharmacogenetic testing for health insurance companies and payers is cost-saving through the reduction of expensive medical interventions resulting from adverse drug reactions. Pharmacogenomics can also lead to better medication adherence, reducing healthcare costs in the long term.

What Companies Provide Pharmacogenomic Testing?

Finally, I will give you a short list of companies that currently provide pharmacogenomic testing with some basic information such as company description and cost of testing. Obviously, the cost of pharmacogenomic testing is something that changes overtime. So, please take this information with grain of salt.

23andMe: Pharmacogenetic Report

23andMe is probably the most famous direct-to-consumer genetic testing company and among the range of genetic tests it provides, it includes pharmacogenetic testing. 23andMe Pharmacogenetic test as part of its 23andMe + Membership package. It is important to note that 23andMe's pharmacogenetic tests have not been reviewed by the FDA, and the company advises that you should not change your medication regimen based on their results. More info about 23andMe pharmacogenetic testing can be found here, here and here.

Myriad Genetics: GeneSight Psychotropic Test

Myriad Genetics acquired Assurex Health in 2016 and effecitvley became owner of the GeneSight Psychotropic Test. GeneSight test analyzes how your genes may affect your response to medications commonly prescribed for depression, anxiety, ADHD, and other psychiatric conditions. The GeneSight test is not FDA approved, and the cost varies depending on your insurance coverage, but can range from $0 to $330. More about how much GeneSight pharmacogenomic test might cost you can be found here.

Color Genomics: Color Medication Response Genetic Test

Color Genomics is a genetic testing company that offers a pharmacogenetic test as part of its broader Color Health service, which analyzes how your genes may affect your response to certain medications. The test is called Color Medication Response Genetic Test The pharmacogenetic test is not FDA approved, and the cost of the Color Health service is $249 plus shipping. Color Medication Response Genetic Test reports gene drug interactions for 12 genes which includes multiple genotypes and halpotypes per gene. These are the genes that are included according to the latest documentation: CYP2D6, CYP2C19, CYP3A4, CYP1A2, CYP2C9, CYP3A5, CYP4F2 , DPYD (More about DPYD gene here), F5, IFNL3 , NUDT15 , SLCO1B1, TPMT, VKORC1.

OneOme: RightMed Test

OneOme is a pharmacogenetic testing company that offers the RightMed test, which analyzes your DNA to determine how you may respond to over 340 medications. The RightMed test is not FDA approved, and the cost is $349. More information can be find here and here.

Genomind: Genomind® Professional PGx Express™

Genomind is a personalized medicine company that offers a pharmacogenetic test called the Genomind Professional PGx Express, which analyzes how your genes may affect your response to medications commonly prescribed for psychiatric conditions. The Genomind test is not FDA approved, and the cost varies depending on your insurance coverage, but can range from $0 to $399.


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