Pharmacogenetics Testing

One of the questions that puzzle your health care provider, especially those who treat cancer, is why some drugs work better for some patients but have no effect in others with the same cancers. Many cancer medications must be “switched on” to work. This turning on of a drug is known as activation, which is facilitated by enzymes. If the enzymes do not respond, the therapy will not be effective in fighting cancer.  Pharmacogenomics can provide oncologists opportunities to personalize cancer treatments for their patients and has been used for many years to do so.  Oncologist battle with the burden of addressing the many side effects that oncology medications can produce such as nausea, pain, depression, neuropathy, and infections.  It is crucial for these patients to obtain optimization of their medication therapies so that responses to their oncology medication yield the most benefit.  Supporting evidence is abundant for the utilization for pharmacogenomic (PGx) testing by oncologists.  Some of the most actionable areas of study for oncology patients can be used when evaluating neuromodulators, antidepressants, pain, and antifungal medications.  Pharmacogenomic results can be utilized all the way through the many stages of oncology treatment including palliative care.  In the final stages of someone’s journey in their battle with cancer, providers want to be able to ensure that medications are effective in providing relief to their patients. Pharmacogenomic information specific to an individual can aid an oncology health care team in making the most informed decisions about medications for their patients.[7] Pharmacogenomic (PGx) testing may help improve therapeutic benefit in pain management.  The inability to achieve pain control with certain medications can leave some patients struggling, misusing, and discontinuing medications because of undesirable side effects. Through pharmacogenetics (PGX) testing, the healthcare practitioner might find that adjusting dosages or changing therapies may be warranted to optimize medication therapy and avoid undesirable side effects. In addition, if a patient is taking pain medicine and getting little relief, there can be tendency on the patient’s part to increase the dosage leading to the potential abuse of the medication. This can lead to toxic levels of the drug in the body increasing the likelihood of addiction, and possible overdose. Pharmacogenomic (PGx) testing can help mitigate the threats of these complications and simplify the choices of medications for patients. An example of where pharmacogenomic (PGx) testing can provide insight on the metabolism of pain medications is with the CYP2D6 enzyme.  Medications such as hydrocodone, oxycodone, tramadol, and codeine are all affected from the metabolizing actions of CYP2D6.  Having pharmacogenomic information on this enzyme in pain management can provide insight if a patient should even begin these therapies or change these therapies reducing the risk of unwanted side effects or abuse of opioids.  Pharmacogenomics is not limited to opioids treatments, there is also supporting pharmacogenomic evidence with NSAIDS where CYP2C9 or CYP2C8 are major contributors to their metabolism.  Polymorphisms from these CYP450 enzymes can all contribute to difficulties in drug selection for pain management patients and utilized as a standard of care in this space.[8]

Psychiatry is one of the most profoundly affected areas of study in pharmacogenomics.  When beginning therapy for any mental health condition it is well documented that most therapies can take four to six weeks to provide relief from mental health symptoms.  Many times, healthcare practitioners are forced to use the trial-and-error method for selecting medications.  This can slow the progress of relieving the symptoms patients may be experiencing or potentially increase symptoms in the process of beginning new therapies.  This is where pharmacogenomic (PGx) testing can provide a more focused direction for patients being treated with mental health conditions.  To better predict how a patient will react to medications in mental health it is important for a patient’s healthcare provider to have knowledge of how the metabolism of medications can be affected by their genetics.  For example, selective serotonin reuptake inhibitors (SSRI) are a commonly prescribed class of antidepressants for individuals battling with depression and anxiety disorders.  The enzymes CYP2D6 and CYP2C19 can both contribute to the metabolism of SSRI’s which can lead to a patient potentially experiencing unwanted side effects or no benefit at all.  Since medications like SSRI’s can take up to four to six weeks to achieve any therapeutic benefit, it is of the utmost importance to initiate the most effective therapy to start.  Pharmacogenomic (PGx) test results are crucial in selecting the right medication for mental health patients and can be revisited repeatedly to make the most informed decision about their medications. [9]

Cardiology treatments are yet another area that pharmacogenomic (PGx) testing that can provide insight on drug selection for patients.  There are many therapies used for the treatments of hypertension, stroke, and heart attack that can be affected by a patient’s metabolism of certain medications.  For example, clopidogrel (Plavix) is a common platelet P2Y12 receptor inhibitor prescribed to decrease plaque buildup in the arteries ultimately preventing patients from having a cardiac event like a heart attack.  Clopidogrel is unique in its metabolism by CYP2C19 in that it requires activation by this enzyme. Therefore, if a patient has poor metabolizing function of CYP2C19, clopidogrel is not able to be activated in the body and cannot provide any protection against having a heart attack.  The FDA drug label for clopidogrel warns that patients that are identified as poor CYP2D19 metabolizers should begin other anti-antiplatelet therapies not metabolized by CYP2D19. [10]