As said in the previous section, chlorpromazine was the first drug developed to treat psychotic symptoms in patients with schizophrenia.  Since then, similar compounds have been synthesized. All of these drugs are known as “typical” antipsychotics because they were the first type of antipsychotic drugs developed (they are the typical kind of antipsychotic). All of these drugs appear to be somewhat equally effective at reducing psychosis  (Kane et al 1988, in Perry 2002).   However, 20 to 30% of people with schizophrenia do not respond to long-term treatment with these drugs (Kane et al 1988, in Perry 2002).

What  are Other Typical  Antipsychotics Developed After  Chlorpromazine?

        (1) Fluphenazine (Prolixin)
        (2) Haloperidol  (Haldol)
        (3) Molindone
        (4)Thioridazine (Mellaril)
        (5)Trifluoperazine  (Stelazine)

  What is the Mechanism by which  Typical Antipsychotic Drugs Decrease Psychosis?

       Now we know that all typical drugs act by blocking dopamine receptors in several areas of the brain, thus preventing dopanime from transmitting messages from neuron to neuron (read about dopamine and neurotransmitters).    In order for these drugs to block the receptor, they must be similar to dopamine or at least have a certain degree of affinity   to  the receptor.    One may think of affinity as the degree of “matching” between two molecules, as if they were puzzle pieces; the better they match, the higher their affinity. This is why researchers say that typical antipsychotic drugs have a high affinity to dopamine D2 receptors, which is one of several types of dopamine receptor (Carlson 2001, Alexander 1996).

                                             

          How can researchers tell that these drugs decrease psychosis by decreasing dopamine activity in the brain?  There is evidence supporting this theory. For instance,   it has been  shown that the antipsychotic power of a drug - how effective the drug is at decreasing psychosis- is correlated to its affinity to D2 receptors. In other words, the more “matching” between a drug and dopamine receptors, the  better the drugs does at decreasing psychosis.  This suggests that  psychosis in schizophrenia is reduced as the activity of  this neurotransmitter is decreased. Also, there is evidence showing that people may develop psychosis when using drugs that promote or increase dopamine activity in the brain, such as amphetamines and cocaine (read more about amphetamines).