Let's move on to treatment of psychotic disorders. So we have
a very long list. So I am going to divide up the classical
drugs into drug classes for you. The phenothiazine, the
thioxanthenes and the butyrophenones. Okay, the classic
antipsychotic drugs have high antidopamine or dopamine receptor
activity. These drugs the first ones work at the D2 receptor.
They are more effective and they have fewer metabolic side effects than the newer agents,
but are more likely to cause extrapyramidal side effects.
They are very very well absorbed. They cross the blood brain barrier easy
which I think is very important for a disease that occurs
mostly in the brain. They have very long half lives.
Now I will mention too that they do have interactions with
the cytochrome system and so patients who are taking cytochrome
inhibitors will have a prolonged action and perhaps even a
toxic reaction with these medications. These drugs take some
time to have an effect. And all of them block histamine
receptors except for haloperidol. Looking at the novel agents
used in psychotic disorders, you can see that the novel agents
are very similar to the novel agents being used in bipolar
disease. Novel agents act through both dopamine and serotonin
receptors. That's what makes them a little bit different.
Generally speaking, you are going to get fewer extrapyramidal
side effects than the classic drugs. Clozapine is a D4 and
5HT2 blocker. Olanzapine is a weak D2 inhibitor and a strong
serotonin 2A agent. And this agent has multiple effects.
The newer agents effectiveness have led to a new theory: The
serotonin hypothesis of schizophrenia. So we used to talk about
psychosis being exclusively a dopamine kind of mediated disease
but because we see that these new agents have anti-serotonin
or serotonin effect, we now have added serotonin to our
understanding of how schizophrenia works. So let's talk about
the use of antipsychotics in schizophrenia. Antipsychotics
reduce the positive symptoms of schizophrenia. Antipsychotics
have few effects on the negative symptoms. Clozapine is
effective in refractory cases and newer agents are more effective
than the older cases in what we call "negative symptoms". So
what do we mean by positive and negative symptoms. A positive
symptom is something that seems very aggresive and overt to you.
So it's those people who perhaps maybe violent or verbally abusive.
Negative symptoms are the anhedonic kind of reactions where they
don't enjoy anything, they become withdrawn, we call those negative.