Effect of a Single Dose of the SSRI Fluoxetine on motor Activation Patterns of the upper Extremity in Chronic Stroke Survivors

Background: Clinical studies indicate that the use of selective serotonin reuptake inhibitors (SSRIs), amphetamine, or methylphenidate may be beneficial to increase motor output. Using SSRIs, it is possible to modulate cortical excitability. The objective of the present study is to explore the effect of a single dose of the SSRI fluoxetine on muscle activation patterns, i.e., muscle output and cocontraction.Methods: 10 chronic stroke survivors were included in a double-blind crossover trial. Patients were given 20 mg fluoxetine or placebo after baseline assessments
on day 1 and 2, respectively. Follow-up assessments were performed 5 h after intake of fluoxetine. The order of drug administration was randomized. Outcome measures used were isometric EMG output of both wrist flexors and extensors. Clinical outcome measures were the motricity index and grip strength.Results: RMS of both wrist flexors and extensors of theimpaired limb increased significantly (F = 8.052, P < 0.01). Delay times were not different after intake of fluoxetine.Cocontraction appears to be slightly less after fluoxetine, but the difference was not significant. Grip strength of the paretic arm was lower after fluoxetine.Conclusion: Although motor output increased significantly, no improvement in delay in initiation and termination was found. Neither did we see a significant
reduction in cocontraction. The findings suggest that it is possible to enhance motor output using a single dose of fluoxetine, but that selectivity is not improved.