What Are Atypical Neuroleptics?

H. Colledge

Neuroleptics are tranquilizing drugs used in the treatment of psychosis, where delusions and hallucinations are associated with psychiatric disorders such as schizophrenia. Even at normal doses, typical neuroleptics tend to cause troublesome side effects of muscle spasms and involuntary movements, known as extrapyramidal symptoms. Atypical neuroleptics can be used to treat psychosis without extrapyramidal side effects, although side effects can occur later or may develop at higher doses. One of the best known atypical neuroleptics is a drug called clozapine. Not all researchers agree on which neuroleptics should be described as atypical.

Olanzapine and risperidone belong to the family of atypical antipsychotic drugs.
Olanzapine and risperidone belong to the family of atypical antipsychotic drugs.

The main use of neuroleptics is to treat psychosis by calming the emotions, reducing hallucinations and delusions, and decreasing confusion and agitation. Other uses of neuroleptics make use of their sedative effects and include the treatment of conditions such as hiccups and nausea. Of the different types of neuroleptics, the powerful drug halperidol is a well-known example from the typical group. Atypical neuroleptics include clozapine, risperidone and olanzapine. Even though they are less likely to cause extrapyramidal symptoms, they may cause other side effects such as diabetes, weight gain and a condition known as agranulocytosis, where the number of white blood cells falls.

Weight gain is a possible side effect of atypical neuroleptics.
Weight gain is a possible side effect of atypical neuroleptics.

Of all the atypical neuroleptics, clozapine is the drug which has been researched most extensively. It is effective in treating psychotic symptoms, with a much lower risk of causing extrapyramidal side effects compared with typical neuroleptics. Extrapyramidal side effects typically include spasms called dystonias, occurring in a single muscle or a group of muscles. Dystonias may be repetitive or prolonged and, in some cases, painful. The other group of extrapyramidal side effects are involuntary movements, or dyskinesias, which typically appear quite strange and could be either rhythmic or chaotic in nature.

Unfortunately, the use of clozapine is limited by its association with agranulocytosis. In this condition, the bone marrow does not produce enough of the white blood cells that form part of the body's immune response, leaving patients vulnerable to infection. This means that clozapine may be reserved for patients who do not find typical neuroleptics effective. Other atypical neuroleptics have occasionally been associated with agranulocytosis, but they more commonly cause problems such as weight gain and diabetes.

The safety of neuroleptics depends on doctors carefully monitoring patients while they are taking the drugs. This allows any side effects to be detected and remedied as soon as they occur. While atypical neuroleptics are relatively new, and information about them is still being collected, over all they seem to have less severe side effects than the typical group of drugs.

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