5 min49910:48 pmby Ryan Freeman

A Quick Pharmacogenomics Definition 

Pharmacogenomics combines pharmacology, or the science of how drugs work, with genomics, which is the science of the human genome. Pharmacogenomics is a field of research that looks at how your genetic makeup affects the way you respond to medication. 

The study of pharmacogenomics allows your doctor to choose the safest and most effective drugs and drug dosages for you, based on information in your DNA. Through pharmacogenomics, your doctor can pinpoint medications that could affect you negatively, and eliminate them from your treatment plan. We’ll take a closer look at this in a moment.

What is Pharmacogenomics? A More In-Depth Pharmacogenomics Definition

The development of modern medicine is one of the most important advancements in the 21st century. Every day, countless lives are saved by administering drug therapy to patients in need. However, sometimes the treatments don’t have their desired effect. And in some cases, patients can even experience negative effects, known as adverse drug reactions (ADRs). 

Until recently, companies developed medications with the idea that each one works identically for everyone. The thought was that one medication would have the same effect on everybody. That is not the case. Luckily, genomic research has changed that “one size fits all” approach and opened the door to more personalized development and usage of drugs.

To put it a different way, here’s an analogy:

One-size-fits-all clothing is a lie. It sounds harsh, but it’s true. Clothing brands market one-size-fits-all all the time. Many brands even have the best intentions at heart, such as supporting body positivity and inclusivity in the clothing industry. But one-size-fits-all just doesn’t exist. There’s no way that a pair of pants can possibly fit everyone. That’s because humans are unique. There is no cookie-cutter template for normal, despite society pushing for there to be. Fortunately, major steps have been taken to banish the one-size-fits-all mindset, and more brands are embracing the differences in the human body.

Clearly, one-size-fits-all is an outdated concept. So why are we still applying it to our medicine? 

Why aren’t there more medicines that cater to our individual needs? Everyone is different. So why should our medications all be the same outside of different dosages? 

In general, medications work how they’re supposed to, but sometimes they don’t. Pharmacogenomics is all about decreasing the risk of medications not working as intended. 

Many Factors Contribute to How People Respond to Drug Treatment

These factors include:

  • infection
  • exercise
  • disease
  • stress
  • fever
  • alcohol intake
  • smoking
  • age
  • gender
  • ethnicity
  • pregnancy
  • occupational exposures
  • concomitant drugs
  • circadian and seasonal variations
  • diet
  • cardiovascular function
  • etc.

These contributors to drug response can be variable and unreliable. However, one factor has proven that it can be used to reliably prescribe medication to patients. That factor is genetics.

The main goal of pharmacogenomics is to limit drug toxicity while optimizing drug efficacy based on an individual’s DNA. When a gene variant is associated with a particular response to a drug, doctors can potentially make clinical decisions based on that information. 

The most common gene variants associated with drug response are single-nucleotide polymorphisms or SNPs (pronounced: snips). A SNP is a variation within a DNA sequence when a single nucleotide (adenine, thymine, cytosine, or guanine) is altered. SNPs may influence drug toxicity and effectiveness.

Depending on your genetic makeup, some drugs may work more or less effectively for you than they do for other people. Likewise, some drugs may produce more or fewer side effects for you than for someone else. In the near future, pharmacogenomics will allow doctors to routinely use information about your genetic makeup to tailor your individual drug prescriptions by dose, possible side effects, and effectiveness.

How does pharmacogenomics work?

First, it all starts with genes. Genes are instructions written in our DNA for constructing proteins. Different versions of the same gene exist in different people, and each version has its own slightly different DNA sequence. These different versions are called gene variants. Some variants are rarer than others. Also, just as some genes determine our eye and hair color, others affect how we respond to medication.

Drugs interact with our bodies in a multitude of ways. These interactions depend on the dosage of the drug and where the drug acts in the body. After you take a drug, your body needs to break it down and get it to where it needs to be.

These processes are heavily influenced by proteins. Certain proteins directly affect how medications work in our bodies by playing key roles in drug reception, uptake, breakdown, and removal. Pharmacogenomics focuses on the gene variants that code for these proteins. 

Scientists first identify a gene sequence that is associated with known drug responses. This is done by genome sequencing large groups of people who suffer from the same ADR’s. Once the genomes are sequenced, scientists then narrow down the possible gene variants until they find the one(s) responsible for the ADR.  Then, after a gene sequence is identified, doctors can test their patients to see if they have that specific gene variant. Based on those results, doctors can determine whether or not a patient will have an adverse reaction to certain drugs.

The Process

1) DNA collection. Once authorized by a healthcare provider, the patient uses a saliva or buccal sample collection kit to provide their DNA. There are many DNA collection methods, but the buccal method, where an  individual swabs their cheek, is superior to just spitting in the collection tube. 

2) Sending your DNA out for sequencing. The individual mails the kit to a genetic laboratory where scientists then analyze the DNA using scientific testing. Scientists usually test DNA using multigene analysis or whole-genome single nucleotide polymorphism (SNP) profiles. 

3) DNA assessment. After 3-4 weeks, the laboratory makes the results of your genomic profile available for your physician to view and assess. From this information, the physician can make clinical suggestions. *See below for an example* 

A Pharmacogenomics Example:

All people have a liver enzyme called CYP2D6. This enzyme plays an important role for many prescription drugs, such as the painkiller codeine (also known as morphine in its active form). CYP2D6, like all proteins, is coded by a gene. There are around 160 variants of the CYP2D6 gene, and some of them affect how the liver enzyme CYP2D6 acts. One variant of the CYP2D6 gene creates too much of the CYP2D6 enzyme, and this leads to the body processing medication too quickly.

Consequently, someone with that variant of the gene may turn codeine into morphine so quickly that a standard dose could be an overdose. On the other hand, some individuals may have a CYP2D6 gene variant that produces an ineffective liver enzyme. These individuals may process codeine slowly or not at all, so codeine is not an effective painkiller for them.

With pharmacogenomics, doctors will be able to detect these CYP2D6 gene variants in advance. Therefore, if a patient has a medical condition that requires the administration of codeine, the doctor will be able to make informed decisions based on that patient’s genome.

The Bottom Line

By using information about your genetic makeup, doctors soon may be able to avoid the trial-and-error approach of giving you various drugs that are ineffective until they discover the right one. With pharmacogenomics, you can find the “best-fit” drug for you from the beginning.

Find out more on pharmacogenomics at omnipgx.com!

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