Genetic testing to choose the right antidepressant

Psychiatrists often try two or more medications in a patient suffering with major depression before settling on the one that seems to work best for that individual.  Sometimes, after several are tried and abandoned, two (or even three) are used in combination.

Medication selection is part of the art of psychiatry, but, now, testing is available that promises to make it more of a science.  A company called AssureRx Health now offers what it calls GeneSightRx—“pharmacogenomic” laboratory testing that helps identify which antidepressants are a good match for a person’s genetic makeup, and which are not so good a match.

Sometimes, the testing reveals why three or four antidepressants haven’t worked for a patient, while pointing in the direction of one that might.

This is extremely good news, because psychiatrists have several different kinds of antidepressants to choose from—some which increase the activity of the brain chemical messenger serotonin, some which increase the activity of the brain chemical messenger norepinephrine and some which increase both.  And they do so by varying mechanisms, requiring the activity of different enzymes.

The technology behind GeneSightRx actually determines which genetic variants—in terms of the enzymes that are activated by antidepressants—a person possesses.

Different antidepressants affect the enzymes very differently.  Hence, the testing can literally predict with some accuracy which antidepressants are likely to work in a particular person, and which are likely to cause the fewest side effects.

Recent studies have revealed that antidepressants don’t work much better than placebo medications (sugar pills) for many patients.  But those studies weren’t conducted by first selecting patients who are more likely (as determined by GeneSightRx) to respond to the particular medicine being studied.

It’s very possible that patients given medications “suggested” by such testing would do far better than those given placebos—because they aren’t being lumped together and given one medicine, regardless of their individual genetic makeup.

Moreover, since many patients discontinue their antidepressants due to side effects like sexual dysfunction and sleeplessness, choosing a medication that is metabolically and genetically less likely to cause these and other side effects makes good sense.

GeneSightRx also predicts which ADHD medications, antipsychotics and pain medications patients are likely to respond to and from which they are likely to experience fewer side effects.

The GeneSightRx test requires only that a patient swab the inside of his or her cheek and submit the sample directly to the company.  Currently, the company offers financial assistance to make the test affordable for almost any commercially insured individual with household income less than $150,000.  Those with household income above that—whose insurance companies do not cover the whole fee for testing—would pay an increased amount (on a sliding scale).

Pharmacogenomic testing like this—far from taking decision-making away from psychiatrists—actually equips psychiatrists to make more informed decisions.  It certainly could help anyone who has been treated with one antidepressant that didn’t work (and now needs to try another).  And for anyone who has tried a few, it would seem pretty smart to take the test before going on a third.

I have already started using these tests in my practice, and find them to be extremely helpful.