Antipsychotic drugs

Antipsychotics Overview

  • Definition: Antipsychotic drugs, also known as neuroleptics or antischizophrenic drugs, are used primarily in treating schizophrenia, acute mania, and other acute psychotic states.

Psychoses vs. Neuroses

  • Psychoses: Major mental issues where insight is lost, judgment is affected, and disturbances in mental function may occur, e.g., schizophrenia.

  • Neuroses: Minor mental issues with preserved insight and judgment; disturbances are rare.

Types of Antipsychotic Drugs

First Generation (Typical) Antipsychotics

  • Examples: Chlorpromazine a (prototype), Haloperidol, Thioridazine.

  • Side Effects: Tardive dyskinesia, sedation, akathisia.

Second Generation (Atypical) Antipsychotics

  • Examples: Clozapine, Olanzapine, Risperidone, Aripiprazole.

  • Characteristics: Less extrapyramidal side effects, effective in treating schizophrenia and mood disorders.

Symptoms of Psychosis

  • Core Symptoms:

    • Diminished capacity to process information

    • Delusions and hallucinations (auditory, visual)

    • Incoherence or disorganized behavior

    • Aggression

Dopaminergic Systems in Schizophrenia

  • Mesolimbic-Mesocortical Pathway: Closely related to behavior and psychosis.

  • Nigrostriatal Pathway: Coordination of voluntary movement; blockade leads to EPS.

  • Tuberoinfundibular System: Regulates prolactin release; dopamine inhibits secretion.

Dopamine and Serotonin Hypotheses

  • Dopamine Hypothesis: Excess dopaminergic activity can lead to psychosis; antipsychotics block D2 receptors to alleviate symptoms.

  • Serotonin Hypothesis: 5-HT2A receptor blockade is key in atypical antipsychotic mechanisms; regulates dopamine and other neurotransmitters.

Mechanisms of Action

Typical Antipsychotics

  • Block D2 receptors; higher occupancy leads to EPS.

Atypical Antipsychotics

  • Greater blockade of 5-HT2A than D2 receptors; lower risk of EPS.

Clinical Uses

  • Primary Indication: Schizophrenia.

  • Other Uses: Mood disorders, schizoaffective disorders, psychotic depression, mania in bipolar disorder, Tourette's syndrome, disturbed behaviors in Alzheimer's.

Adverse Effects

  • Extrapyramidal Symptoms (EPS): Parkinsonism, akathisia, tardive dyskinesia; more common with first-generation.

  • Metabolic Effects: Weight gain, hyperglycemia; notable with second-generation antipsychotics.

  • Other Reactions: Autonomic effects, endocrine disruptions, toxic reactions.

Drug Interactions

  • Caution with sedatives, anticholinergics, and other drugs affecting dopamine.

Notable Antipsychotic Examples

  • Haloperidol: Effective but causes EPS.

  • Clozapine: Used for resistant schizophrenia; side effect includes agranulocytosis.

  • Olanzapine: Effective for schizophrenia and mania; side effects include weight gain and metabolic disturbances.