meta-Fluoxetine is an isomer of fluoxetine that is found as an impurity in fluoxetine preparations. meta-Fluoxetine is a weaker serotonin selective reuptake inhibitor (SSRI) than fluoxetine, in which the trifluoromethyl group is at the para position (Kis = 166 and 17 nM, respectively, in rat brain synaptosomes).