Depressed? Genetics affect how drugs work
September 17, 2017 | By Steve Dorfman
Twenty-first century “precision medicine” is all about genetics — especially when it comes to treating depression and mental illness with medication.
Thanks to the relatively new field of pharmacogenomics — which the National Human Genome Research Institute defines as the use of “information about a person’s genetic makeup to choose the drugs and drug doses that are likely to work best for that particular person” — doctors can potentially bypass some of the “trial and error” phase traditionally inherent in prescribing antidepressant medication.
“This is a new frontier and still in the early stages — but appears to be very promising for depression sufferers,” said Boca Raton, Florida, psychiatrist Dr. Barnell Phillips, who is also medical director of Archstone Recovery Center of the Palm Beaches in Lantana.
An estimated 20 million Americans suffer from a depressive disorder — and Phillips noted there are multiple challenges in prescribing antidepressant medication(s) for them.
Among the variables:
— Which of the three drug “classes” to prescribe (each class works on a different neurotransmitter — either serotonin, norepenephrine or dopamine)?
— Which class is most likely to mitigate the patient’s most severe symptoms?
— How can side effects (gastric distress, headaches, weight gain and loss of libido, among others) be avoided or limited?
— How will the antidepressant interact with other medication(s)?
“I’m assessing both how the medication affects the patient’s body — and how the patient’s body affects the medication,” explained Phillips.
The advent of pharmacogenomics puts another device in the physician’s toolbox.
Using a small sample of a patient’s blood, doctors can run cytochrome P450 (CYP450) tests to help determine how a patient’s body processes and metabolizes drugs, Phillips said.
How quickly or how slowly a patient metabolizes medicine will have a potential impact on the medication’s efficacy and the severity of side effects.
“I can look at a patient’s CYP450 numbers and then look at the collective patient data of a medication I’m considering to see how that medication interacted with people who had a similar CYP450 profile,” said Phillips.
Genetic testing facilities nationwide are going a step farther, enabling patients and doctors to test multiple specific genes associated with the class of drugs the doctor is considering — and then offering recommendations.
For instance, if a doctor is considering prescribing a selective serotonin reuptake inhibitior (SSRI) to treat depression, anxiety or personality disorder, Pathway Genomics will analyze five specific genes (CYP2D6, CYP3A4, SLC6A4, CYP2C19, HTR2A) and then offer predictive guidance as to which medication(s) in what dosages are most likely to be effective.
Likewise, in a recent study performed by the Mayo Clinic, the symptoms of patients with depression who had medications prescribed to them based on the findings/recommendations of GeneSight’s psychotropic testing were reduced 70 percent more effectively than patients who were prescribed antidepressants without genetic testing.
Industry experts believe that, as genetic testing evolves, pharmaceutical companies will use that data to create more targeted psychotropic medications.
And that’s good news to physicians like Phillips, who emphasized the need to not only eliminate a patient’s symptoms, but also prevent recurrence.
“My goal is to put my patients’ depression in full remission — just like an oncologist wants to do with cancer.”