Antipsychotics have been in use since the 1950s. The earlier (conventional) types of antipsychotics were effective in treating positive symptoms (abnormal thoughts and perceptions, such as delusions, hallucinations or disordered thinking). However, they had the potential to produce many unpleasant side effects, such as muscle stiffness, tremors and tardive dyskinesia (involuntary movements that may include tongue thrusting, repetitive chewing, jaw swinging and/or facial grimacing).

In the 1990s a new type of antipsychotics, atypical antipsychotics, was introduced. These antipsychotics are effective at treating both positive and negative symptoms (absence of thoughts and behaviors that would otherwise be expected). Examples of negative symptoms include lack of emotion, speech, social interaction and movement.

The first type of atypical antipsychotic introduced in the United States in 1990 was clozapine, which proved to be effective in treating disorders that did not respond to conventional antipsychotics. The risk of tardive dyskinesia was lower with clozapine than with earlier types of antipsychotics.

However, the use of clozapine results in the risk of a side effect called agranulocytosis (blood disorder that causes loss of white blood cells that fight infection). Therefore, patients  taking clozapine must have a blood test performed every one to two weeks, which may be costly and inconvenient.

Several other atypical antipsychotics were introduced after clozapine, including risperidone, olanzapine, quetiapine and ziprasidone. There are side effects associated with each of these, but they are generally better tolerated than the conventional types of antipsychotics.

The following is a list of the different types of antipsychotics:

Pimozide (whose brand name is Orap) is an antipsychotic used to treat Tourette’s syndrome (an abnormal condition characterized by verbal outbursts, tics and other movements, such as eye blinks or facial twitches, which cannot be controlled).

In December of 2006, the U.S. Food & Drug Administration approved the use of paliperidone (Inviga) extended-release tablets to treat patients with schizophrenia. The drug is a new molecular entity, which contains a substance that has never been marketed before in the United States.