Schizophrenia

Pharmacotherapy for Schizophrenia

Overview

  • Module: Pharmacology and Theranostics (P&T) - Unit 6: Psychiatric and neurological disorders

  • Instructor: Dr. Cristina R Reschke, Senior Lecturer, School of Pharmacy and Biomolecular Sciences.

Learning Outcomes

  • Understand the symptoms, diagnostic criteria, risk factors, and pathophysiology of schizophrenia.

  • List the different classes of antipsychotics used in the treatment of schizophrenia.

  • Discuss the mechanisms of action, pharmacokinetics, and adverse effects of antipsychotics.

  • Describe novel therapeutic approaches and non-pharmacological treatments for schizophrenia.

What is Psychosis?

  • Definition: Psychosis refers to a set of symptoms where an individual's mental capacity to recognize reality is impaired.

Schizophrenia and Psychosis

  • Distinction: Psychosis does not always equate to schizophrenia.

  • Schizophrenia Characteristics:

    • A complex and heterogeneous chronic psychiatric disorder characterized by:

    • Delusions: Fixed beliefs that are often bizarre, lacking rational basis, and resilient to contrary evidence.

      • Example: Paranoid delusions such as the belief in being recruited by a government agency.

    • Hallucinations: Perceptual experiences across all sensory modalities that occur without an external stimulus, commonly auditory examples such as hearing voices.

Depiction of Schizophrenia

  • Case Study: A Beautiful Mind depicts mathematician John Nash's struggle with paranoid schizophrenia, including his delusions and visual hallucinations.

Symptom Classification

  • Symptoms of schizophrenia can be categorized into three groups:

    • Positive Symptoms: Hallucinations, delusions, disorganized speech/behavior.

    • Negative Symptoms: Decreased emotional expression, motivation, and social cognition impairment.

    • Cognitive Symptoms: Attention deficits, concentration issues, and short-term memory impairment.

Epidemiology of Schizophrenia

  • Prevalence: Approximately 1% of the global population is affected.

  • Life Expectancy: Individuals may experience a reduction in life expectancy by 10-20 years.

  • Unemployment Rate: High unemployment rate, approximately 80-90% of affected individuals.

  • Social Impairment: Difficulty in maintaining social relationships and living independently.

  • Suicide Risk: Elevated risk of suicide, estimated at 12 times higher than the general population.

Risk Factors for Schizophrenia

  • Multifactorial Etiology:

    • Advanced paternal age

    • Maternal infections during pregnancy

    • Birth during winter months

    • Genetic predisposition

    • Life adversities and drug abuse

    • Living in urban environments

Pathophysiology of Schizophrenia

  • Classic Dopamine Hypothesis: Focuses on hyperactivation of dopamine pathways, specifically the mesolimbic pathway:

    • Dopamine Theory: Hyperactive dopamine at D2 receptors contributes to positive symptoms.

    • Glutamate Hypothesis: NMDA receptor hypofunction may underlie symptomatology.

    • Serotonin Theory: Hyperfunction of 5HT2A receptors in the cortex may also contribute to the disorder.

Neurotransmitter Pathways Linked to Psychosis

  • Mesolimbic Pathway:

    • Projects from the ventral tegmental area (VTA) to the nucleus accumbens, regulating motivation and reward.

    • Hyperactivity of this pathway relates to positive symptoms of psychosis.

  • Mesocortical Pathway:

    • Hypoactivity mediates cognitive, negative, and affective symptoms of schizophrenia.

Additional Pathways

  • Nigrostriatal Pathway: Primarily associated with motor control, remains normal in untreated schizophrenia.

  • Tuberoinfundibular Pathway:

    • Regulates prolactin release; normal functioning is critical for end hormonal balance.

Treatment Strategies for Schizophrenia

  • Goals of Treatment: Minimize symptoms, functional impairments, side effects, and promote recovery with an emphasis on self-determination and social integration.

Pharmacotherapy Approaches

  • First-Generation (Typical) Antipsychotics: Primarily target D2 receptors, associated with extrapyramidal side effects and worsening negative symptoms.

  • Second-Generation (Atypical) Antipsychotics: Target both D2 and 5HT2A receptors, have a more favorable side effect profile.

    • Efficacy: Atypical agents are the first-line treatment choice due to lower rates of extrapyramidal symptoms.

    • Key Drug: Clozapine – noted for the best efficacy but carries a risk of agranulocytosis and other severe side effects.

Adverse Effects of Antipsychotic Medications

  • Common Side Effects:

    • Extrapyramidal Effects: Include parkinsonism, akathisia, dystonia, and tardive dyskinesia, arising primarily from D2 receptor blockade.

    • Hyperprolactinemia: Caused by the blockade of D2 receptors in the tuberoinfundibular pathway, leading to increased prolactin levels.

    • Anticholinergic Effects: Due to muscarinic receptor blockade, resulting in cognitive dysfunction and physical symptoms (constipation, dry mouth).

    • Weight Gain: Significant concern with several atypicals, requiring metabolic monitoring (weight, triglycerides, glucose, BP).

Uniqueness of Specific Drugs

  • Aripiprazole: D2 partial agonist with minimal extrapyramidal effects, widely used due to its safer profile.

  • Pimavanserin: Functions as a 5HT2A antagonist with proven antipsychotic efficacy but does not interact with D2 receptors.

  • Cariprazine: D2 and 5HT1A partial agonist, approved for both schizophrenia and acute bipolar mania, with particular efficacy for negative symptoms.

Long-Acting Injectable Formulations

  • Formulations: Injectable versions of risperidone, paliperidone, and aripiprazole offer compliance solutions.

  • Use Case: Effective in treating non-compliant patients or crisis situations requiring rapid intervention.

Conclusion

  • Key Takeaway Messages:

    • Schizophrenia is a severe chronic mental disorder with complex symptoms.

    • Pathophysiology is tied to dysregulated dopaminergic function, along with receptor interactions.

    • Atypical antipsychotics remain the first-line treatment due to a generally safer side effect profile.

    • Monitoring for adverse effects is essential for effective management and ensuring patient safety.