Antipsychotic Drugs, Atypical

(redirected from Atypical Antipsychotic Drugs)

Antipsychotic Drugs, Atypical



The atypical antipsychotic agents, sometimes called the "novel" antipsychotic agents are a group of drugs which are different chemically from the older drugs used to treat psychosis. The "conventional" antipsychotic drugs are classified by their chemical structures as the phenothiazines, thioxanthines (which are chemically very similar to the phenothiazines), butyrophenones, diphenylbutylpiperadines and the indolones. All of the atypical antipsychotic agents are chemically classified as dibenzepines. They are considered atypical or novel because they have different side effects from the conventional antipsychotic agents. The atypical drugs are far less likely to cause extra-pyrammidal side-effects(EPS), drug induced involuntary movements, than are the older drugs. The atypical antipsychotic drugs may also be effective in some cases that are resistant to older drugs.
The drugs in this group are clozapine (Clozaril), loxapine (Loxitane), olanzapine (Zyprexa), and quetiapine (Seroquel).


The antipsychotic drugs are used to treat severe emotional disorders. Although there may be different names for these disorders, depending on severity and how long the symptoms last, psychotic disorders all cause at least one of the following symptoms:
Loxapine has also been used to treat anxiety with mental depression.

Recommended dosage

The recommended dose depends on the drug, the patient, and the condition being treated. The normal practice is to start each patient at a low dose, and gradually increase the dose until a satisfactory response is achieved. The odse should be held at the lowest level that gives satisfactory results.
Clozapine usually requires doses between 300 and 600 milligrams a day, but some people require as much as 900 milligrams/day. Doses higher than 900 millgrams/day are not recommended.
Loxapine is usually effective at doses of 60-100 milligrams/day, but may be used in doses as high as 250 mg/day if needed.
Olanzapine doses vary with the condition being treated. The usual maximum dose is 20 milligrams/day.
Quetiapine may be dosed anywhere from 150-750 milligrams/day, depending on how well the patient responds.


Although the atypical antipsychotics are generally safe, clozapine has been associated with severe agranulocytosis, a shortage of white blood cells. For this reason, people who may be treated with clozapine should have blood counts before starting the drug, blood counts every week for as long as they are using clozapine, and blood counts every week for the first 4 weeks after they stop taking clozapine. If there is any evidence of a drop in the white blood count while using clozapine, the drug should be stopped.
Atypical antipsychotics should not be used in patients with liver damage, brain or circulatory problems, or some types of blood problems.

Key terms

Anxiety — An abnormal and overwhelming sense of apprehension and fear often marked by physiological signs (as sweating, tension, and increased pulse), by doubt concerning the reality and nature of the threat, and by self-doubt about one's capacity to cope with it.
Delusions — A false belief regarding the self or persons or objects outside the self that persists despite the facts.
Depression — A state of being depressed marked especially by sadness, inactivity, difficulty with thinking and concentration, a significant increase or decrease in appetite and time spent sleeping, feelings of dejection and hopelessness, and sometimes suicidal thoughts or an attempt to commit suicide.
Glucocorticoid — Any of a group of corticosteroids (as hydrocortisone or dexamethasone) that are anti-inflammatory and immunosuppressive, and that are used widely in medicine (as in the alleviation of the symptoms of rheumatoid arthritis).
Psychosis — A serious mental disorder characterized by defective or lost contact with reality often with hallucinations or delusions.


People who have had an allergic reaction to one of the atypical antipsychotics should not use that medication again. However, sometimes it is possible to use a different drug from the same group safely.


The atypical antipsychotics have not been proved safe in pregnancy. They should be used only when clearly needed and when potential benefits outweigh potential hazards to the fetus. These drugs have not been reported in human milk.

Side effects

Although the atypical antipsychotics are less likely to cause involuntary movements than the older antipsychotic drugs, they still have a large number of adverse effects. The following list is not complete. Review each drug individually for a full list of possible adverse effects.


Taking atypical antipsychotic medications with certain other drugs may affect the way the drugs work or may increase the chance of side effects. While taking antipsychotic drugs, do not take any other prescription or nonprescription (over-the-counter) drugs without first checking with a physician.
Because the atypical antipsychotics may cause lowering of blood pressure, care should be used when these drugs are taken at the same time as other drugs which lower blood pressure.
Quetiapine has many interactions. Doses should be carefully adjusted when quetiapine is used with ketoconazole, itraconazole, fluconazole, erythromycin, carbamazepine, barbiturates, rifampin or glucocorticoids including prednisone, dexamethasone and methylprednisolone.
These drugs will also require dose adjustments when used with anti-Parkinson medications.



Brain Basics: An Integrated Biological Approach to Understanding and Assessing Human Behavior. Phoenix: Biological-Psychiatry-Institute, June 1999.


McDougle, C. J. "A double-blind, placebo-controlled study of risperidone addition in serotonin reuptake inhibitor-refractory obsessive-compulsive disorder." Archives of General Psychiatry August 2000: 794.
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
Serotonergic blockade by atypical antipsychotic drugs in schizophrenic patients causes an increase in the release of dopamine.
Popadak et al., "H1-histamine receptor affinity predicts short-term weight gain for typical and atypical antipsychotic drugs," Neuropsychopharmacology, vol.
This patient illustrates that NMS can occur due to treatment with atypical antipsychotic drugs like olanzapine, particularly in the presence of risk factors.
Minimizing cardiovascular adverse effects of atypical antipsychotic drugs in patients with schizophrenia.
Metabolic syndrome and cardiovascular disease are important causes of morbidity and mortality among patients with severe mental illnesses receiving atypical antipsychotic drugs. There is a need for formulation of guidelines for screening, monitoring and managing the patients on antipsychotics in general and atypical antipsychotics in particular for potential metabolic problems.
Shankar, "Minimizing cardiovascular adverse effects of atypical antipsychotic drugs in patients with schizophrenia," Cardiology Research and Practice, vol.
Sachdev, "Neuroleptic malignant syndrome associated with atypical antipsychotic drugs," CNS Drugs, vol.
(2.) Trollor JN Chen X and Sachdev PS (2009) Neuroleptic malignant syndrome associated with atypical antipsychotic drugs. CNS Drugs 23:477-492
It is known that the frequency of TD can be reduced with gradually increasing the usage of atypical antipsychotic drugs. High efficiency in the treatment of psychosis together with fewer side effects of atypical antipsychotic drugs are generally related with dopaminergic blockage in the mesolimbic pathway rather than the nigrostriatal pathway and increased dopamine release due to serotoninergic blockage in the nigrostriatal pathway (6).
Findings from another study using Medicaid data found that children in areas underserved by child psychiatrists are likelier to be prescribed atypical antipsychotic drugs for nonpsychotic conditions than in areas where more child psychiatrists practice.
CONCLUSION: The consequences of excessive weight gain (obesity) associated with atypical antipsychotic drugs are likely to include poor compliance or even discontinuation of therapy by the patients.
Medicines and Healthcare products Regulatory Agency (MHRA): Atypical Antipsychotic Drugs and Stroke; 2004.