The feeling you are getting is not quite serotonin syndrome related, but rather a somewhat unique combination of neurons re-regulating their activity as a result of the olanzapine withdrawal and the effects of the aripiprazole. I find aripiprazole fascinating due to its mechanism(s) of action to be quite honest, and its a rather ingenious pharmaceutical when used appropriately. There is another similar drug I have yet to investigate (though I have forgotten the name,) but outside of these two newer atypical antipsychotics there have not been many great options for treatment of certain sets of mental disorders that have been developed thus far. Its a very promising class of pharmaceuticals and I cannot wait to see where it leads, but to get to answering your question now (apologies for side-tracking.)
The olanzapine was strongly blocking dopamine’s action at the D2 receptors, and now you have discontinued it abruptly so a rebound effect is being experienced. Plus, being that aripiprazole acts as a partial agonist at D2 receptors which means it is also boosting the dopaminergic activity that is already in overdrive. This is likely what is causing talkativeness and the mild euphoria you feel. It should be an almost stimulant like effect from this aspect of your situation.
Both olanzapine and aripiprazole affect the serotonin receptors, but in a different way. Olanzapine is a strong antagonist at 5HT2A and 5HT2C receptors which would contribute to the increase in energy/boosted mood you may feel due to the withdrawal. Aripiprazole affects the 5HT1A receptors as a partial agonist which should be giving a mild feeling of anxiety relief similar to MDMA (feeling of melting as some may describe it.) The effect at 5HT2 receptors is weaker than olanzapine, so it only slightly blocks the effects of withdrawal here which somewhat mediates the aforementioned rebound effects relative to 5HT2A receptor re-regulation. Collectively this could elicit an empathogenic effect or a feeling of being more connected with others and/or animals for example.
MDMA primarily increases serotonin release and, to a lesser extent, dopamine and norepinephrine. The combination of dopaminergic rebound from olanzapine withdrawal and aripiprazole’s partial agonist activity at serotonin and dopamine receptors could mimic mild MDMA effects, such as euphoria, increased energy, and a sense of well-being.
So, in summary, the overlap between dopamine and serotonin system modulations by aripiprazole and the rebound effects from olanzapine withdrawal likely explain the MDMA-like feelings. These effects highlight the importance of gradual medication changes to avoid such unintended and potentially destabilizing experiences.
Honestly, whoever switched the meds this rapidly was doing a somewhat poor job as a psychiatrist, but I figure it was an honest mistake. Psychiatrists are often overworked and stressed due to the demands of the job they hold, but that should be no excuse. However, I myself sometimes slip up as I did earlier this evening when discussing pharmacology in a group setting. But, seeing as I was the most educated person in the room regarding such at that point in time there was no uproar. However, I know I made the mistake myself so I will take note, correct my mistake internally, and if it comes up again remember my fault. This is how most people operate, and as I said before: the psychiatrist will likely work with you if your mood doesn’t stabilize in about two weeks or so as your brain adjusts to the rapid shift in medications. Try not to make any major decisions until this time; that is the best advice I have at this time for you considering your current situation.
Hope all works out well for you once things settle!!
P.S. I am exhausted after having gotten only 4 hours of sleep last night and still being awake now due to writing an essay with supporting evidence backing my opinion on why drugs should be legalized and regulated for the sake of both the lives of both drug users and society as a collective which I just got done presenting to a group and having a lengthy discussion thereafter. I hope you will understand if there are any minor errors in grammar or repetitions of facts as I was having some difficulty with linear thinking at points during my explaining the above, though I hope I did correct the mistakes when I reviewed everything. Thank you for your patience with me on this matter; it is greatly appreciated