Have you ever been prescribed a medication by a doctor, but it didn't work for you, even though it worked for a friend? Or have you ever had side effects that only you get from certain medications that others don't? You may have wondered, "Why doesn't this medication work for me?" Have you ever thought that the reason for this could be your genes? Isn't it amazing? Yes, these tiny genes inside our bodies can completely change the way a medication we take works. Today we're talking about one of the newest and most important fields of medicine. That's Pharmacogenomics.
Simply put, what is Pharmacogenomics?
This word is a bit long and seems difficult, doesn't it? But let's break it down. Then it's very easy. It's made up of two words put together.
1. Pharmacology: This refers to the study of medicine . That is, how a medicine is used, what it does to the body, and what its effects are.
2. Genomics: This refers to the study of genes and their function .
So when these two come together, Pharmacogenomics is the study of how our genes respond to the drugs we take. Simply put, it's about finding out how well a drug you're given will work, or whether it can cause side effects, based on your genetic makeup.
This belongs to a new field of medicine called "Precision Medicine." It means "specific medicine." Instead of giving everyone the same medicine, it takes into account factors such as your genes, your lifestyle, and the environment you live in, and chooses a treatment that is specifically suited to you . Think of it like going to a store and buying a dress that is the same size for everyone, instead of going to a tailor and having a dress made to your own measurements. This is the same.
Currently, this method is used for only a limited number of diseases and drugs. For example, this technology is used for HIV, some types of cancer, depression, and some drugs for heart disease. But this field is developing very quickly. Researchers believe that in a short time, pharmacogenomics will help doctors choose the most suitable drugs for even the most common diseases.
How do our genes affect medications?
To understand this, we first need to look at what genes do in our bodies. Think of our genes as a complete instruction manual for building and operating our bodies. The cells in our bodies work according to the instructions in this instruction manual.
One of the main things these instructions do is make protein molecules called enzymes . Enzymes are like little workers in our bodies. These workers have thousands of jobs. One of the most important of these jobs is to break down, or metabolize, the drugs we take.
Imagine you take a pill. It doesn't go straight to cure the disease. That pill first has to go to the factories inside our bodies (for example, the liver), where the workers there (i.e. enzymes) break it down, break it down, and make it usable by the body.
Now imagine, what happens if these enzymes don't work properly due to genetic variations in some people?
- If the enzymes work too fast: The medicine you take, before it can be absorbed and affect the disease, is broken down and excreted from the body very quickly. Then the normal dose is not enough for you. The medicine will feel like it is not working.
- If the enzymes work too fast: The medicine you take breaks down too fast in your body. Then the medicine builds up in your body in a high concentration. This can cause you to overdose on even the normal dose and have severe side effects .
- If the enzyme doesn't work at all: Sometimes, due to a genetic mutation, the body can stop producing the enzyme in question. Then the medicine may not work at all for you.
That's how even small changes in our genes can have a big impact on the medications we take.
What test is used to detect these genetic changes?
We call this a pharmacogenomic test . This is also a genetic test. It looks at your DNA and looks for any changes in one or more specific genes that affect how a drug breaks down.
This test usually uses a blood sample or a buccal swab . It's very simple. Your doctor sends this sample to a laboratory. Technicians there check your DNA for changes in the relevant genes.
Your doctor will decide which genes to test for based on your medical condition and the type of medication they plan to give you.
In what situations is a pharmacogenomic test necessary?
This test is not currently performed for every disease or every medication. However, your doctor may recommend this test when treating certain specific conditions. Let's look at some examples. To understand this information more clearly, see the table below.
| Medical condition | Relevant gene/enzyme | Impact and simple explanation |
|---|---|---|
| High cholesterol | SLCO1B1 gene | People with certain variants of this gene may experience severe muscle pain and weakness when taking statin drugs (e.g., Simvastatin, Atorvastatin) to lower cholesterol. If this is detected early in the test , your doctor may be able to prescribe a different medication. |
| Depression | CYP2D6 and CYP2C19 genes | These genetic variations change the rate at which some antidepressants are broken down in the body. For some, the medication works very well. For others, it causes more side effects. This test can help choose the most effective medication with the fewest side effects . |
| Cancers | Various genes (e.g. HER2, TPMT, UGT1A1, DPD) |
|
| Preventing blood clots | CYP2C19 gene and others | The blood thinner warfarin needs to be given at very low doses in people with certain genetic variants. Also, the drug clopidogrel (Plavix®) may not work at all in some people due to a variation in the CYP2C19 enzyme. |
| HIV infection | HLA-B and CYP2B6 genes | People with a specific variant of the HLA-B gene can have a severe skin reaction if given the drug Abacavir. Therefore, this test is mandatory before giving this drug. |
| Immune system problems | TPMT, NUDT15, CYP3A5 | After an organ transplant, such as a kidney transplant, the effectiveness of immunosuppressive drugs (e.g., Azathioprine, Tacrolimus) depends on these genes. Changes in these genes can also increase the risk of the body rejecting the transplanted organ . |
What are the advantages of this method?
As the field of Pharmacogenomics develops, we will benefit greatly.
- Safer treatments: Doctors can identify medications that can cause serious side effects or overdose in some people, so they can avoid those medications and give you the safest medication .
- Efficiency and cost reduction of treatment: Imagine, you have to switch 3-4 medicines for a disease, and finally find the right medicine. Until then, your time, money, and effort are wasted. And you suffer until the disease gets better. But if this test can cure the disease with the first medicine given , how great would that be?
- Targeted drug development: Some diseases are caused by changes in a specific gene. So researchers can develop new drugs that directly target the changes in that gene . This is very important in treating diseases like cancer.
But this has its limits...
No matter how good this method is, it doesn't solve everything. When choosing a drug, a doctor doesn't just think about genes. There are many other factors to consider.
The important thing is, your genes are only one part of the story. There are many other things that affect how a drug works.
A doctor should also be concerned about other factors such as:
- Other medications you are currently taking: A medication you are taking for one condition and another for another condition can affect your body in a way that causes it to break down.
- Other medical conditions you have: For example, if you have liver or kidney problems, it can affect the way the medicine is eliminated from the body.
- Your lifestyle: What you eat and drink, whether you exercise or not, and even things like smoking and alcohol use can affect how well your medication breaks down.
In addition, there are several other challenges:
- Cost: Although the cost of these genetic tests is gradually decreasing, they may still be too expensive for some people to afford.
- Inaccessibility: Facilities for conducting these tests are not yet available everywhere in Sri Lanka. They are available only in a few limited places.
However, this field of "Precision Medicine" is developing very rapidly. If you have any questions about this, don't be afraid to talk to your doctor . Ask him or her if there is any benefit to having this type of test for your condition.
Take-Home Message
- Pharmacogenomics is simply the study of how your genes affect the medications you take.
- Through this method, your doctor can choose the safest and most effective medication for you.
- This is still a developing field. It is currently used to treat a few specific diseases, such as HIV, cancer, and depression.
- It's not just your genes that determine whether a drug will work for you. Your lifestyle, other medications you take, and other medical conditions also play a role.
- If you have any questions about this, the best and most appropriate person to talk to is your doctor.
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