Antipsychotic Drugs

Chlorpromazine

Class: First-generation (typical).

Mechanism: Strong D₂ receptor blockade.

Other receptors: H₁, muscarinic, and α₁ blockade.

Uses: Schizophrenia; useful when psychosis is associated with insomnia due to sedation.

Adverse effects:

Sedation and drowsiness (H₁ blockade).

Anticholinergic effects: dry mouth, blurred vision, constipation, urinary retention.

Orthostatic hypotension (α₁ blockade).

EPS due to D₂ blockade.

Hyperprolactinemia.

High-yield clues: Sedating antipsychotic; high anticholinergic effects; orthostatic hypotension.

Haloperidol

Class: First-generation (typical).

Mechanism: High affinity for D₂ receptors; low affinity for D₁.

Uses: Schizophrenia and psychosis.

Adverse effects:

High risk of EPS.

Acute dystonia.

Parkinsonism-like symptoms.

Tardive dyskinesia (especially with long-term use).

Hyperprolactinemia.

High-yield clues:

Strong D₂ blocker.

High EPS risk.

More motor adverse effects than second-generation drugs

Thiothixene

Class: First-generation (typical) antipsychotic.

Mechanism: D₂ receptor antagonism (class mechanism).

Important note: Mentioned in the lecture’s MCQs.

High-yield: Typical antipsychotic; expect EPS risk from D₂ blockade.

Clozapine

Class: Second-generation (atypical).

Mechanism:

Higher affinity for D₁ than D₂.

Blocks 5-HT₂A, H₁, muscarinic, and α₂ receptors.

Low D₂ affinity.

Uses:

Treatment-resistant schizophrenia.

Schizophrenia with suicidal or self-injurious behavior.

Adverse effects:

Minimal EPS.

Weight gain and metabolic syndrome.

Marked sedation (H₁ blockade).

Anticholinergic effects.

Orthostatic hypotension.

High-yield clues:

Drug of choice for treatment-resistant schizophrenia.

Minimal EPS.

High sedation and weight-gain risk.

Olanzapine

Class: Second-generation (atypical).

Mechanism: D₂ and 5-HT₂A receptor blockade.

Uses: Schizophrenia.

Adverse effects:

Weight gain.

Metabolic syndrome.

EPS risk generally lower than typical antipsychotics.

High-yield: Remember weight gain; second-generation antipsychotics have increased metabolic risk.

Risperidone

Class: Second-generation (atypical).

Mechanism: D₂ and 5-HT₂A receptor blockade.

Uses:

Schizophrenia.

Agitation and restlessness in elderly patients.

Adverse effects:

Hyperprolactinemia.

EPS can occur due to D₂ blockade.

Metabolic adverse effects.

High-yield clues:

Agitation/restlessness in elderly patients.

Can cause hormonal adverse effects through tuberoinfundibular pathway blockade.

Quetiapine

Class: Second-generation (atypical).

Mechanism: D₂ and 5-HT₂A receptor blockade.

Uses: Schizophrenia; also used in bipolar disorder.

Adverse effects:

Sedation.

Weight gain and metabolic syndrome.

Low EPS risk.

High-yield: One of the atypical antipsychotics with particularly low EPS risk.

Aripiprazole

Class: Third-generation antipsychotic.

Mechanism:

Partial agonist at dopamine D₂ receptors.

Dopamine–serotonin system stabilizer.

Uses: Schizophrenia and other psychiatric disorders.

Adverse effects:

Reduced EPS compared with typical antipsychotics.

Reduced hyperprolactinemia.

Lower metabolic and weight-gain risk.

High-yield clues:

Partial D₂ agonist, NOT a full antagonist.

Reduces prolactin secretion.

Exception to the weight-gain tendency of second-generation antipsychotics.

Low risk of me

Tagm3at

1. A 55 years old man is having Parkinson's and he is on levodopa, he started

hallucinating and he started having confusion. What antipsychotic drug should

he take ?

A. Haloperidol

B. Chlorpromazine

C. Clozapine

D. Risperidone

Answer: C

2. Which one of the dopamine pathways elicit the prolactin secretion and has

hormones side effects

A. Mesolimbic pathway

B. Mesocortical pathway

C. Nigrostriatal pathway

D. Tuberoinfundibular

Answer: D

3.A 22-year-old female was presented with schizophrenia that is resistant to typical treatment, her doctor prescribed her medicine that increased her weight. Which of the following drugs can cause this?

A. Chlorpromazine

B. Haloperidol

C. Clozapine

D. Thiothixene

Answer: C

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4.Which one of the following drugs causes weight gain?

A. Chlorpromazine

B. Haloperidol

C. Quetiapine

D. Thiothixene

Answer: C

5.What’s the mechanism of action of Antipsychotic drugs?

A. Agonist on D2 receptors

B. Block D2 receptors

C. Block D1 receptors

D. Agonist on D1 receptors

Answer: B

❄Remember: all 2nd generation drugs can cause weight gain except for aripiprazole

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