The Experience of Schizophrenia

This chart is a result of PET scan studies done by Dr. Shitij Kapur and Dr. Phillip Seeman in Toronto. Ideally you want to prescribe an antipsychotic so that Dopamine D2 occupancy is between the red and green horizontal line, roughly between 65% and 80% of the Dopamine D2 receptors. If you block a higher precentage than 80% you get unbearable side effects. If you block less than 65% you're not getting a therapeutic dose. Kapur and Seeman looked at Haldol, Olanzapine and Rsiperidone to see what the therapeutic threshold is. The light blue shaded area shows the threshold dose. Generally the older you are the higher the dose of antipsychotics needed to prevent symptoms and there can be considerable individual variation in how much medication someone needs to reach between 65% and 80% occupancy. What is very striking about this research is how little Haldol is needed, 2mg daily. It was not uncommon to prescribe Haldol at doses of 20mg daily which will obviously be way too much for most patients.

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general receptor occupancy charts of atypicals