Pharmacogenetic (PGx) testing can provide answers as to why a medication may or may not be working for someone. This can impact the choice and dosing of some medications, potentially leading to dose adjustments or switching to another medication. Currently, PGx testing is used in various medical subspecialties, ranging from autoimmune disorders (immunology) to pain management, to inform dosing of different medications. Within each health specialty, there are different genes that are known to influence individuals’ responses to certain medications.
Autoimmune disorders and PGx
Autoimmune disorders are a set of conditions which are caused by the body mistakenly attacking itself and can have a range of symptoms and age of onset. Typically, autoimmune disorders are treated with immunosuppressant medications which alter the immune system response.
Currently, there are a few immunosuppressant medications that have clinical PGx guidelines, including thiopurines and tacrolimus. The effectiveness and potential side effects of these medications may be predicted by genetic variation in NUDT15, TPMT and CYP3A5.
Blood clotting and PGx
Blood clotting is the process of blood thickening and cells clumping together to stop bleeding in the body. This process helps us when we have a cut or scrape to make sure the wound heals, and we do not bleed too much. However, too much clotting can cause problems such as blocking blood flow through the veins (thrombosis) to important parts of the body.
Typically, excessive blood clotting is treated with anticoagulants and antiplatelet medications. Currently, there are a few antiplatelet and anticoagulant medications that have clinical PGx guidelines, including clopidogrel and warfarin. The effectiveness and potential side effects of these medications may be predicted by genetic variation in CYP2C19, CYP2C9 and VKORC1.
Cancer and PGx
In cancer, medications are used to either target growth of a tumour or of cancer cells or to help patients manage symptoms they experience along with their diagnosis.
Currently, there are a few medications used in the treatment and management of cancer that have clinical PGx guidelines, including thiopurines (immunosuppressants), opioids (medications that help with pain) and anti-nausea medications. The effectiveness and potential side effects of these medications may be predicted by genetic variation in NUDT15, TPMT and CYP2D6.
Digestive health (gastroenterology) and PGx
Gastroenterology is a field of medicine that focuses on digestive health and includes many different symptoms and conditions. Medications play a key role in supporting digestion and relieving discomfort. Some examples of medications for digestive health are proton pump inhibitors (PPIs), which help to control stomach acid, or anti-nausea medications.
Currently, there are a few PPIs and anti-nausea medications that have clinical PGx guidelines, including omeprazole, pantoprazole, lansoprazole and dexlansoprazole (PPIs) and ondansetron and metoclopramide (anti-nausea). The effectiveness and potential side effects of these medications may be predicted by genetic variation in CYP2C19 and CYP2D6.
Heart care (cardiology) and PGx
Cardiology is a field of medicine that focuses on the heart. Medications for heart care work to ensure the heart is beating strong and at the speed it is supposed to. Some examples of medications for heart care are statins, which help to lower cholesterol, and antiarrhythmics, medications that regulate heartbeat.
Currently, there are a few medications used in the treatment of the heart that have clinical PGx guidelines:
- Statins
- atorvastatin
- simvastatin
- lovastatin
- pravastatin
- rosuvastatin
- fluvastatin
- atorvastatin
- Antiarrhythmics
The effectiveness and potential side effects of these medications may be predicted by genetic variation in SLCO1B1, CYP2C9 and CYP2D6.
Infectious disease and PGx
Infectious diseases are illnesses that include viruses, fungal infections, bacterial infections and parasites. Some examples of medications used to treat infectious diseases are antifungals, that help to kill fungal infections, and medications to help treat viruses such as human immunodeficiency virus (HIV).
Currently, there are a few medications used to treat infectious diseases that have clinical PGx guidelines, including abacavir and efavirenz (HIV treatments), and voriconazole (an antifungal). The effectiveness and potential side effects of these medications may be predicted by genetic variation in HLA, CYP2C19 and CYP2B6.
Mental health (psychiatry) and PGx
Mental health is about our overall mental well-being—how we think, feel and handle things in life. Everyone’s mental health is different, and what helps one person might not help someone else. Some examples of mental health medications include antidepressants, which help with feeling sad or anxious; antipsychotics, which help to regulate mood; and others.
Currently, there are many medications used to treat mental health conditions that have clinical PGx guidelines:
- Antidepressants
- Selective serotonin reuptake inhibitors (SRRIs)
- citalopram
- escitalopram
- fluvoxamine
- paroxetine
- sertraline
- citalopram
- Tricyclic antidepressants (TCAs)
- amitriptyline
- clomipramine
- desipramine
- doxepin
- imipramine
- nortriptyline
- trimipramine
- amitriptyline
- Selective norepinephrine reuptake inhibitors (SNRIs)
- venlafaxine
- venlafaxine
- Serotonin modulator and stimulators (SMSs)
- vortioxetine
- vortioxetine
- Selective serotonin reuptake inhibitors (SRRIs)
- Antipsychotics
- Typical/first-generation antipsychotics
- haloperidol
- pimozide
- zuclopenthixol
- perphenazine
- haloperidol
- Atypical/second-generation antipsychotics
- aripiprazole
- risperidone
- brexpiprazole
- clozapine
- aripiprazole
- Typical/first-generation antipsychotics
- Non-stimulant ADHD medications
- atomoxetine
- atomoxetine
The effectiveness and potential side effects of these medications may be predicted by genetic variation in CYP2C19, CYP2B6, and CYP2D6.
Neurological disorders (neurology) and PGx
Neurological disorders are a set of conditions that affect the nervous system, which is made up of the brain, spinal cord and nerves. An example of medications for neurological conditions are anticonvulsants, which help to treat seizures.
Currently, some anticonvulsants and medications used to treat nerve disorders have clinical PGx guidelines, including fosphenytoin/phenytoin, carbamazepine, oxcarbazepine, clobazam and brivaracetam (anticonvulsants), and tetrabenazine and pitolisant (for nerve disorders). The effectiveness and potential side effects of these medications are associated with genetic variation in CYP2C19, CYP2C9, HLA and CYP2D6.
Pain management and PGx
Pain is a common symptom of many illnesses and injuries. Medications such as non-steroidal anti-inflammatory drugs (NSAIDs) are often used to treat pain. Opioids are often used to treat severe pain.
Currently, some medications used to treat and manage pain have clinical PGx guidelines, including celecoxib, flurbiprofen, ibuprofen, meloxicam and piroxicam (NSAIDs), and codeine, tramadol and hydrocodone (opioids). The effectiveness and potential side effects of these medications may be predicted by genetic variation in CYP2C9 and CYP2D6.
Other medications
PGx testing is not limited to the health specialties listed above. As research in PGx evolves, the number of medications that have established recommendations to help guide medication prescribing and treatment decisions using PGx testing will increase.
Currently, there are a few medications used to treat and manage other health conditions not previously mentioned that have clinical PGx guidelines, including allopurinol (a medication that reduces acid in urine used to treat gout), abrocitinib (a medication used to treat inflammation in eczema), and treatments for certain genetic metabolic disorders. The effectiveness and potential side effects of these medications may be predicted by genetic variation in HLA and CYP2D6, respectively.