Are Your Prescribed Medications Actually Right For You? The Power of Pharmacogenomics Explained

Have you ever wondered why the exact same medicine helps your friend feel better right away, but gives you bad side effects or simply does not work at all?

Every person is unique, and our bodies process treatments differently because of our genes. Today, we will explore an exciting field of medical science called pharmacogenomics that helps explain why this happens.

By looking closely at how your body responds to medical treatments, this approach helps your doctor find the best care plan possible.

What Is Pharmacogenomics?

Simply put, pharmacogenomics is the study of how your genes influence your body's response to medicines. Pharmacology is the study of how medicines work in the body. This genomics is the study of genes and their functions. Pharmacogenomics combines these two areas into one powerful medical tool, sometimes called pharmacogenetics.

This science belongs to a larger field known as precision medicine. Precision medicine looks at your unique genes, your daily environment, and your lifestyle to create a customized treatment plan. With pharmacogenomics, your doctor can choose a medicine that gives you fewer side effects and works much better for your specific body.

Right now, this testing is not used for every single health condition or routine medicine. Doctors primarily use it for human immunodeficiency virus (HIV), specific cancer types, depression, and heart conditions. As research moves forward quickly, experts hope this method will help guide treatments for many more common health issues soon.

How Do Genes Affect Medicine Response?

Think of your genes as an instruction book that tells your body cells how to build various proteins. These genes help create molecules called enzymes that perform thousands of essential jobs inside your body. One major job of these enzymes is breaking down medicines so your body can process them properly, a process known as metabolism.

If your body breaks down a medicine too fast, too slow, or not at all, normal standard doses may not work as intended. When this happens, a standard dose might cause severe side effects or provide zero relief for your current illness.

For example, some people can drink a cup of coffee and fall asleep right away. This others feel completely unaffected. This happens partly because our genes control how fast our bodies break down caffeine. Medicines in our bodies follow this exact same rule.

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What Is a Pharmacogenomic Test?

A pharmacogenomic test is a specific type of genetic test that examines one or more of your genes. It looks for specific genetic variants that control how your body processes medicines, checking your personal instruction book for any errors.

Your doctor will usually collect a small blood sample or use a gentle cotton swab inside your cheek, called a buccal swab. The medical team sends this sample to a specialized laboratory where technicians examine your deoxyribonucleic acid (DNA) for specific variations.

The exact genes tested depend entirely on what your doctor orders, the health condition being treated, and the specific medicine you might need. This test gives your clinical team valuable insights to keep your treatment safe and effective.

When Might You Need a Pharmacogenomic Test?

You might be able to get a pharmacogenomic test if you are taking medicines for certain health conditions. Here are several common examples where these genetic tests can provide helpful guidance for your care plan.

High Cholesterol.

Some people carry specific variants in the SLCO1B1 gene that increase their risk of muscle pain and weakness when taking statin medicines for high cholesterol. Common statin medicines include atorvastatin (Lipitor), fluvastatin (Lescol), lovastatin (Altoprev), pitavastatin (Livalo), pravastatin (Pravachol), rosuvastatin (Crestor), and simvastatin (Zocor).

Your doctor can discuss this genetic test with you before starting these treatments or if you experience unusual muscle discomfort while taking them.

Depression.

Variations in the CYP2D6 and CYP2C19 genes can change how quickly your body processes antidepressant treatments. These medicines include amitriptyline (Elavil), which is a tricyclic antidepressant, selective serotonin reuptake inhibitors (SSRIs) like citalopram (Celexa), escitalopram (Lexapro), sertraline (Zoloft), paroxetine (Paxil), and fluvoxamine (Luvox), as well as serotonin-norepinephrine reuptake inhibitors (SNRIs) like venlafaxine (Effexor).

Testing can be very helpful when starting these medicines or when switching from one treatment to another because it is not working well.

Cancers.

If you receive treatment for certain types of cancer, a pharmacogenomic test can help ensure your safety and treatment success. Consider these important clinical examples:

• Breast cancer: Trastuzumab (Herceptin) only works for people who have HER2-positive breast cancer, where cancer cells produce too much HER2 protein due to specific genetic traits.
• Acute lymphoblastic leukemia (ALL): Giving standard doses of mercaptopurine (Purinethol) to people with low levels of the thiopurine methyltransferase (TPMT) enzyme can cause severe side effects and high infection risks.
• Colon cancer: People with low levels of the UGT1A1 enzyme face higher risks of severe diarrhea and infections when taking irinotecan (Camptosar).
• Doctors may also check for low levels of the dihydropyrimidine dehydrogenase (DPD) enzyme before prescribing fluorouracil or 5-FU (Adrucil) for colorectal, breast, stomach, and pancreatic cancers to prevent severe toxic reactions.

Blood Clot Prevention.

People with specific genetic variants often require a much lower dose of the anticoagulant medicine warfarin (Coumadin) to prevent excessive bleeding risks.

also, variations in your liver enzyme CYP2C19 can cause antiplatelet medicines like clopidogrel (Plavix), which helps prevent heart attacks and strokes, to stop working properly in your body.

HIV Infection.

A specific variant in the HLA-B gene can put you at risk for severe, dangerous skin reactions when taking the antiviral medicine abacavir (Ziagen).

Another variant in the CYP2B6 gene can increase your risk of having nervous system side effects when taking efavirenz (Sustiva).

Immune System Issues.

If you take an immunosuppressant medicine to calm your immune system, genetic testing can guide your care:

• Variations in TPMT and NUDT15 proteins can suppress bone marrow activity if you take azathioprine (Imuran) after a kidney transplant or for immune conditions like multiple sclerosis.
• Variations in the CYP3A5 enzyme can increase your risk of organ transplant rejection if you take tacrolimus (Prograf) after receiving a donor organ.

What Are the Benefits of Pharmacogenomics?

As researchers and doctors continue studying pharmacogenomics, this innovative medical field offers several wonderful benefits for patients everywhere.

• Improved safety: Doctors can avoid prescribing medicines that cause dangerous side effects or toxic reactions in your body, sparing you from unnecessary suffering.
• Better efficiency and lower costs: Knowing which treatment works best right away helps doctors prescribe the right option right away, saving you time and money.
• Targeted medicine development: Researchers can design brand new treatments that target specific gene variants directly, creating customized cures for complex diseases.

What Are the Limitations and Disadvantages?

While your genetic makeup plays a massive role in finding the right treatment, it cannot explain every single detail of how your body processes medicines. Your doctor must still consider several other important factors during your evaluation:

• Other medicines: Taking multiple drugs at the same time can change how your body breaks down new treatments.
• Other health conditions: Organ problems, such as reduced kidney function, can cause medicines to stay in your system longer.
• Lifestyle habits: Your daily diet, physical activity levels, tobacco use, and alcohol consumption all influence medicine metabolism.

Other challenges in pharmacogenomics include testing costs and insurance coverage, which can vary widely depending on your health plan and personal budget. Access to these specialized genetic tests may also be limited depending on where you live and your clinical care team.

Right now, doctors can only use pharmacogenomic testing for specific conditions and select medicines. However, precision medicine is expanding rapidly every single day. Talk with your doctor about how pharmacogenomics might benefit your health and ask if clinical trials are available in your area.

A Note From Dr. Priya Sammani.

Quick Comparison of Treatment Approaches.