Antipsychotics I

Introduction

  • Presenter: Yisheng

  • Topic: Antipsychotics, focusing on schizophrenia.

  • Structure: Two-part lecture.

    • Part 1: Introduction to schizophrenia and antipsychotic medications.

    • Part 2: Atypical antipsychotics.

Learning Objectives

  • There are six specific learning objectives outlined for this lecture.

  • Students are encouraged to review these objectives prior to exam preparation.

Psychosis and Schizophrenia

Definition of Psychosis

  • Psychosis is defined as:

    • An impaired relationship with reality.

    • Indicated by a cluster of symptoms rather than a single disorder or syndrome.

Symptoms of Psychosis

  • Symptoms may include:

    • Delusions: Persistent false beliefs.

    • Hallucinations: Sensory experiences without external stimuli.

    • Disorganized thinking: Impaired thought processes affecting behavior.

    • Schizophrenia is highlighted as a specific type of psychosis characterized by significant cognitive disturbance.

Characteristics of Schizophrenia

  • Breakdown of thought processes.

  • Deficit of typical emotional responses leading to cognitive and behavioral responses that are not mood-related.

  • Recognized as a complex and heterogeneous mental disorder with multiple symptoms.

Incidence and Risk Factors

  • Prevalence:

    • Affects approximately 1% of the adult population worldwide.

    • Associated with a high suicide rate; about 25% of those who attempt will succeed.

  • Risk Factors:

    • Genetic predisposition: Having a first-degree relative with schizophrenia increases risk.

    • Environmental factors: Growing up in a tough neighborhood, experiencing trauma, or sustained brain injury can contribute to risk.

    • Medication use: Certain medications can induce symptoms similar to schizophrenia.

Patient Behavior

  • Patients may exhibit:

    • Paranoia and suspicion, often distrusting healthcare providers.

    • High relapse rates; nonadherence to medication can lead to a relapse rate as high as 80%.

  • Economic implications:

    • Addressing schizophrenia incurs high medical expenses.

Symptom Categories

  • Schizophrenia symptoms are categorized into three main groups:

    • Positive Symptoms: Excess symptoms above normal; e.g., hallucinations, delusions, and aggressive behaviors.

    • Negative Symptoms: Deficits in normal emotions and behaviors; e.g., lack of speech, emotional expression, social withdrawal.

    • Cognitive Symptoms: Issues with memory, concentration, and decision-making.

  • Observational behaviors include:

    • Catatonia: Stupor-like states, bizarre behaviors, and neglect of personal hygiene.

Antipsychotic Medications

Overview

  • Two categories of antipsychotics:

    • Typical (First Generation): Dopamine D2 antagonists; e.g., Chlorpromazine (brand name: Thorazine), Haloperidol (brand name: Haldol).

    • Atypical (Second Generation): Not covered in this lecture, to be discussed in part two.

Mechanism of Action

  • Antipsychotics target different dopaminergic pathways in the brain:

    • Nigrostriatal Pathway: Involved in motor function; deficiency leads to Parkinson's disease.

    • Mesolimbic Pathway: Hyperdopaminergic activity in this pathway is linked to psychosis; antipsychotics help alleviate symptoms by blocking dopamine receptors.

    • Mesocortical Pathway: Connects to the cortex; abnormalities can also influence cognitive functions in schizophrenia.

    • Tuberoinfundibular Pathway: Regulates prolactin release; antipsychotics can lead to side effects like hyperprolactinemia.

  • The complexity arises when antipsychotics trying to correct pathway issues may induce side effects in other pathways.

Evidence Supporting the Dopamine Hypothesis

  • The dopamine hypothesis posits that schizophrenia is linked to excess dopamine activity in the mesolimbic system, which is supported by evidence such as:

    • Antipsychotics effectively blocking D2 receptors.

    • Increased dopamine receptor density in postmortem brain tissue of schizophrenics.

    • Dopamine-enhancing drugs may induce psychosis.

  • Important to recognize that the dopamine hypothesis is a simplified model; other neurotransmitters and systems (serotonin, glutamate, etc.) also play significant roles.

Side Effects of Antipsychotics

Side Effects Overview

  • Side effects are often related to the receptor antagonism caused by both typical and atypical antipsychotics.

  • Therapeutic effects primarily address positive symptoms but can also lead to adverse reactions like extrapyramidal symptoms (EPS).

Extrapyramidal Symptoms (EPS)

  • EPS are drug-induced symptoms that can be debilitating:

    • Acute Dystonia: Muscle spasms, locked limbs.

    • Akathisia: Motor restlessness can lead to patient distress or even suicidal ideation.

    • Tardive Dyskinesia: Characterized by involuntary, often irreversible movements; may affect facial muscles, seen after long-term treatment.

    • Risk of developing symptoms related to Parkinson's disease: bradykinesia, rigidity, tremors occur as the dopamine blockade affects nigrostriatal pathway.

    • Neuroleptic Malignant Syndrome (NMS): Rare but serious; characterized by high fever, muscle rigidity, and potentially coma.

Specific Antipsychotic Medications

  • Chlorpromazine (Thorazine):

    • First antipsychotic that revolutionized treatment options.

    • Low potency leads to less EPS but more side effects from its affinity to other receptors (e.g., antihistamine effects leading to sedation or weight gain).

  • Haloperidol (Haldol):

    • High potency; stronger D2 receptor antagonism leads to higher incidence of EPS and hyperprolactinemia.

    • Relatively clean drug, inexpensive and commonly prescribed, effective for acute psychosis.

Conclusion

  • Summary of typical antipsychotics and their effects.

  • Atypical antipsychotics discussed in Part 2.

  • Thank you for your attention, ending Part 1 lecture.