Prozac is a SSRI thus it can block or atleast reduce the effects of certain drugs such as MDMA, LSD, Psilocybin and other psychedelics. As for Seroquel it is a anti-psychotic that is a antagonist of various Serotonin and Dopamine receptors so it will block the effects of serotonics or Dopaminic drugs like Cocaine at anti-psychotic doses. I never found it to block the effect of any opiates though and i am prescribed both Seroquel instant release and Morphine and i still get euphoria from morphine and other opiates.
I still take Coke as well as psychedelics such as psilocybin mushrooms every now and then but i stop taking the Seroquel a few days beforehand. That is not a good practice at all by the way as you should never stop taking a psychiatric drug on your own. But Seroquel has a rather short half life of about 5-6 hours and is not a very potent dopamine antagonist to begin with so laying off it for a few days to let your Serotonin and Dopamine receptors return to normal let's me get the full effects of stimulants and psychedelics.