Serotonin reuptake inhibitor question So this is a pretty specific and possibly dumb question but how is it that drugs like DXM, tramadol and kanna, to name a few, have SRI effects that either are solely responsible or atleast a contributing factor to the feel of them while pharmaceutical SSRIs like prozac and zoloft take time to accumulate before having noticeable effects, if any? Now I have made the distinction between selective SRIs and non selective ones and don't believe this difference is the answer to this question as the same accumulation thing applies to SNRIs and tricyclics. I'm questioning whether this just a baseless excuse from the pharmaceutical industry to make up for the inefficacy of typical antidepressants but I may just be biased. Anyways, any inputs appreciated.