Posted by Iansf on February 8, 2006, at 19:45:30
Psychomotor Speed May Predict Responsiveness to Fluoxetine
News Author: Laurie Barclay, MD
Jan. 27, 2006 — Testing psychomotor speed can determine responsiveness of patients with depression to fluoxetine, according to the results of a study reported in the January issue of the American Journal of Psychology.
"The potential benefits of discovering predictors for individual antidepressants are considerable because patients could be matched to a medication to which they are most likely to respond," write Bonnie P. Taylor, PhD, from the New York State Psychiatric Institute, Columbia University College of Physicians and Surgeons in New York, and colleagues. "Because the first choice of treatment for the majority of depressed patients is a selective serotonin reuptake inhibitor (SSRI), it would also be useful to prospectively identify patients who are likely to be unresponsive to SSRI monotherapy because they could be given some alternative.... The authors hypothesized that since psychomotor slowing in depressed patients has been linked to reduced dopaminergic neurotransmission, patients with slowing would be unresponsive to fluoxetine, an SSRI."
After baseline neuropsychological testing, 37 outpatients with depression completed a 12-week trial of open-label fluoxetine.
Compared with the 25 patients who responded to fluoxetine, the 12 patients who did not respond had significantly poorer verbal fluency on the Controlled Oral Word Association Test FAS (COWAT FAS) and in color naming on the Stroop Color and Word Test. Compared with the responders, the nonresponders also tended to perform worse on the Stroop Color and Word Test reading subtest and on the Wechsler Adult Intelligence Scale–Third Edition (WAIS-III) digit symbol subtest. Both groups had similar performance on tasks of executive functioning, attention, visuospatial functioning, and verbal intelligence, suggesting that differential treatment response was specific to psychomotor speed.
"Psychomotor slowing may identify a subgroup of depressed patients who have a dopaminergic deficit that is unresponsive to fluoxetine monotherapy and who should therefore receive an alternative treatment," the authors write.
Study limitations include open-label design with no placebo control group, lack of generalizability to SSRIs other than fluoxetine, and flexible-dose design possibly leading to an underestimation of the predictive value of psychomotor slowing.
"Prospectively identifying patients who are unlikely to respond to one of the most frequently prescribed antidepressants would guide physicians to initiate treatment with an alternative medication," the authors conclude. "This is critical because it can potentially reduce the time to symptom relief and increase treatment compliance. Furthermore, it can prevent the premature discontinuation of treatment that often results from feelings of hopelessness, helplessness, and frustration due to an ineffective therapeutic response."
Eli Lilly and Co, the maker of fluoxetine, supported this study.
Am J Psychol. 2006;163:73-78
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