Gene Spotlight: 5HTT and antidepressant medications

MedicatedAccording to data from the Centers for Disease Control and Prevention, about one in 10 Americans aged 12 and older takes antidepressant medications.

The majority of these drugs are metabolized by the body’s highly genetically variable CYP2D6 and CYP2C19 pathways. Response to selective serotonin reuptake inhibitors (SSRIs), a commonly prescribed type of antidepressant, may also be affected by variations in the 5HTT gene.

Roughly 40 percent of the North American population carries a 5HTT variation that may make them less likely to respond to SSRIs. 5HTT codes for a protein found in neurons that helps regulate serotonin levels at the main site of action —the same chemicals many antidepressants (includ­ing Prozac and Paxil) target. Genetic variations to 5HTT may decrease the efficacy of these medications.

Genelex added 5HTT testing to its core panel of five CYP tests last year. 5HTT testing is generally not used to predict changes in blood levels of SSRIs. Rather, the testing is best used to help predict future response or tolerance to SSRIs or better understand past or current drug response.

Who would make a good candidate for such a test? In general, prescribers with patients who are starting SSRIs or other therapies targeted at 5HTT, or who are experiencing adverse effects or low efficacy of prescribed SSRIs, should consider 5HTT genotyping.

More specifically, Caucasians with the 5HTT variant that limits serotonin transport may see a better response and decreased adverse drug events with non-SSRI medications compared to treatment with SSRIs. A prescriber may consider adjusting therapy by prescribing a non-SSRI drug for treatment of depression for patients with decreased 5HTT activity.

5HTT joins a list of tests Genelex offers that are geared toward specialized prescribing. These includes HLA-B*5701, which tests for sensitivity to the HIV medication abacavir (Ziagen). Find out more about Genelex’s entire test panel here.