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How Genetic Testing Helps Reduce the Side Effects of Medication
How Genetic Testing Helps Reduce the Side Effects of Medication
Please note that allergies to medications are outside the scope of this article and are
therefore not discussed.
Why medication side effects happen in the first place
Prescription drugs' side effects can occur for a number of reasons.
Side effects may be an extension of the medication's main beneficial effects. For example, a medication used to reduce a fast heart rate may cause it to become slower than hoped for, and this may be associated with side effects like fainting, dizziness, or even worsened heart function.
In other cases, side effects happen because the medication isn't very effective at travelling to the site in the body that is affected and in need of treatment. For example, some individuals will reach for the same pain killer whether they have a headache, or a sore back. The medication often doesn't know to specifically travel to the back, or the head. It goes to both, and many other places, and reduces the symptom in the place affected. However, some of the medication may go to the kidneys as well, contributing to kidney-related side effects.
Other cases may involve the immune system. For example, in some individuals, aspects of their immune system may become triggered and hypersensitive after a few weeks or months of starting specific medications. This can then cause major symptomatic side effects like severe rash over large sections of the body.
Side effects can be caused or influenced by a number of factors, including the dose used, differences in medication metabolism, medical history, individuals' expectations of the medication itself, differences in body weight, sex, age, organ function, food and liquid intake, how the medication is taken or even specific factors at a cellular or "microscopic" level.
Some of these factors can cause medication levels in the body to become too high, resulting in side effects. In some cases, it can be because beneficial effects and side effects tend to happen at the same time and so even normal or lower medication levels can be problematic - this too can be influenced by some of the factors mentioned above.
The role of your genes in how your body processes medication
Factors influencing the frequency and severity of side effects are influenced by genetics, and most people carry variations in genes that affect the way they respond to certain medications. In other words, genetic variations contributing to side effects are very common.
The most well-known example is how specific variations in key genes impact how fast or how slow the medication is metabolized. As a result, medication (or medication byproducts) may build up in the body and cause issues. These issues are often broad and can help explain a number of different side effects experienced with a specific medication across different individuals.
In other cases, genetic deficiencies affecting blood, specific tissues or specific biological processes can predispose individuals to experiencing certain side effects, often more specific in nature. For example, a number of medications can contribute to a type of anemia due to a genetically deficient enzyme found within blood cells.
Common medications where genetics increase side effect risk
There are many examples of well-known or important medications whose side effects are influenced by genetics.
These include certain anti-inflammatories (including ibuprofen, meloxicam and celecoxib) when prescribed for regular, daily use. Over a week or two, genetically "slower" metabolizers are at increased risk of side effects, with changes in blood pressure and kidney function being of particular concern.
Similarly, many common antidepressants side effects can be linked to deficiencies in the genes that influence how they are metabolized.
Some common opioid painkillers (codeine, tramadol) are also affected by metabolism differences due to genetics. However, since these medications need to be made active by a specific metabolism gene, those whose metabolism is "faster" will be at greater risk of the various side effects associated with them, including problematic effects on breathing.
Many antiseizure medications are impacted by genetic variations that impact how parts of the immune system may react to use of these medications. This can contribute to major rashes that can affect a large portion of the body, which, in more severe (but rare) cases, can lead to the skin detaching from the body. Various organs may also be affected.
A specific family of antibiotics (usually given in hospital) can cause hearing loss. Genetic variations in a specific gene in some individuals can "look" like the version seen in bacteria that are the target of the antibiotic, which can then cause hearing damage.
How pharmacogenetic testing predicts side effects before they happen
Pharmacogenetic testing is a process involving an analysis of someone's DNA for variations known to impact side effects (and/or effectiveness) associated with a number of medications. This information can then be used to inform the choice of the medication selected, or the dose, monitoring, or further investigations needed when prescribers select a certain medication with one of the goals being how to reduce side effects of medicines. And while it can't fully answer the question "how to get rid of medicine side effects?", it could meaningfully reduce the occurrence, frequency and/or severity of side effects associated with treatments. It may even help prevent side effects with specific drugs altogether because an alternative not affected by someone's genetic variations has been selected instead.
This could mean that someone can eat the foods they prefer because their antidepressant isn't causing nausea. It could mean that a loved one undergoing a short medical procedure doesn't need to miss a family reunion because they need to stay in hospital for a few days recovering from a prolonged medication effect. It could even mean helping set realistic expectations about the likelihood of muscle pains when starting a statin - a symptom often attributable to many other factors rather than the statin itself. This could mean staying adherent to the medication and reducing the negatively disruptive effects of a future heart attack or stroke on their lives, and of those around them.
What this means for safer and more effective treatment plans
Pharmacogenetic testing provides actionable insights that can support health care providers in their medication treatment decisions. The results help identify which medications or dosing strategies may be less likely to cause problematic side effects based on their genetic profile, allowing them to reduce trial-and-error, stick with their treatment plan, and get the most out of their treatment.
