1. Antipsychotic (Neuroleptic) Drugs
Course Coordinator
Jamaluddin Shaikh, Ph.D.
School of Pharmacy, University of Nizwa
Lecture-27
April 16, 2012

2. Psychosis
Psychosis is a mental disorders characterized by one or more of the following symptoms:
diminished and distorted capacity to process information and draw logical conclusions
hallucinations, delusions, or marked loosening of associations
aggression or violence

3. Antipsychotic Drugs Antipsychotic drugs lessen psychosis
Prescribed for the treatment of mania, some movement disorders, and various types of nonspecific agitated behaviors
However, most frequently employed in the therapy of schizophrenia
Mania: state of abnormally elevated or irritable mood
Agitated behaviors:

4. Schizophrenia
A group of disorders marked by impaired behavioral function, and disturbances of thinking
Characterized by delusions, hallucinations, and thinking or speech disturbances
Often initially affects people during late adolescence or early adulthood and is a chronic and disabling disorder
It has a strong genetic component and probably reflects some fundamental biochemical abnormality
Delusions: psychiatric condition, false belief
Hallucinations: a perception in the absence of stimulus

5. Types of Antipsychotic Drugs
Classification of antipsychotic drugs are:
1. Classical 'typical' antipsychotics
chlorpromazine, haloperidol
2. Recent 'atypical' antipsychotics
clozapine, risperidone

6. Antipsychotic Drugs: Mechanism of Action
Antagonists at dopamine D2 receptors, also block other monoamine receptors, especially 5-HT2
Antipsychotic potency generally runs parallel to activity on D2-receptors, but other activities may determine side-effect profile
Antipsychotics take days or weeks to work, suggesting that secondary effects may be more important than direct effect of D2-receptor block

7. Antipsychotic Drugs: Mechanism of Action
EPS:The extrapyramidal system can be affected in a number of ways, which are revealed in a range of extrapyramidal symptoms (EPS), such as akinesia (inability to initiate movement) and akathisia (inability to remain motionless).

8. Relative Action on Various Receptors
Chlorpromazine
Haloperidol
Clozapine
Risperidone DA
+++
++++ ++
alpha
Muscarinic
5-HT
Histamine

9. Antipsychotic Drugs: Pharmacokinetics
After oral administration, the neuroleptics show variable absorption
Readily pass into the brain
Have a large volume of distribution
Bind well to plasma proteins
Metabolized by the cytochrome P450 system in the liver
Antipsychotic Drugs: Adverse Effects
Side-effects include extrapyramidal motor disturbances and endocrine disturbances
Sedation, dry mouth, blurred vision, hypotension are also common