Home Pharmacology Neuropharmacology Pharmacology of Antipsychotic Drugs

Pharmacology of Antipsychotic Drugs

antipsychotic drugs
#antipsychotic drugs

Summary Points on Antipsychotic Drugs:

Classification of Antipsychotics: Typical (D2 blockers) and Atypical (acting via other mechanisms)

Actions of Typical Antipsychotics:

  • Blocking D2 receptors with differing potency
  • Sedative effects are more common in low-potency drugs
  • Extrapyramidal symptoms more common in high-potency drugs
  • Low anticholinergic and autonomic side effects in high-potency drugs
  • Lower seizure threshold and potential to precipitate convulsions in epileptic patients
  • Potent antiemetic drugs, except for thioridazine
  • Significant α blocking and anticholinergic properties in low-potency drugs
  • Can increase prolactin release resulting in galactorrhoea and amenorrhea

Actions of Atypical Antipsychotics:

  • Antagonistic actions at 5-HT2 and alpha receptors
  • May or may not possess D2 blocking activity
  • Less likely to cause extrapyramidal symptoms
  • Weight gain, hyperlipidemia, and new-onset diabetes mellitus are common side effects, except for ziprasidone and aripiprazole.

Individual Drugs:

  • Thioridazine:
    • Low incidence of extrapyramidal symptoms
    • Interferes with male sexual function
    • Can cause cardiac arrhythmia and retinal damage
  • Trifluperazine, fluphenazine and haloperidol:
    • High potency drugs
    • Marked extrapyramidal symptoms
  • Penfluridol:
    • Longest acting antipsychotic drug
  • Pimozide:
    • Selectively blocks D2 receptors
    • Carries risk of arrhythmias due to QT prolongation
  • Clozapine:
    • Atypical antipsychotic drug
    • Weak D2 blocking action
    • Suppresses positive and negative symptoms of schizophrenia
    • Risk of seizures and agranulocytosis
    • Powerful anticholinergic effects
    • Least risk of extrapyramidal symptoms
  • Risperidone:
    • Blocks 5-HT2, a adrenergic and D2 receptors
    • More potent D2 blocker than clozapine
    • Can cause extrapyramidal symptoms at high dose
    • Risk of hyperprolactinemia
  • Olanzapine:
    • Similar mode of action as risperidone
    • Potent anticholinergic drug
    • Can cause seizures and weight gain
    • Associated with higher risk of stroke and death in elderly patients
  • Ziprasidone:
    • Causes QT prolongation
    • No association with weight gain, hyperlipidemia or diabetes
  • Quetiapine:
    • Can cause cataract formation
    • Shortest half-life
  • Aripiprazole:
    • Acts as a partial agonist at 5-HT1A and D2 receptors
    • Antagonist at 5-HT2A receptors
    • Known as dopamine-serotonin stabilizer
    • Long half-life
    • Approved for treatment of irritability associated with autistic disorders in children
  • Asenapine:
    • Used sublingually for schizophrenia and acute mania
  • Iloperidone:
  • Brexipiprazole and cariprazine:
    • New drugs approved for schizophrenia
  • Pimavanserin:
    • New atypical antipsychotic drug
    • Indicated for oral treatment of hallucinations and delusions associated with Parkinson’s disease.

Adverse Effects:

  • Sedation: maximum with chlorpromazine, minimum with ziprasidone and aripiprazole
  • Weight gain: all except haloperidol; less with ziprasidone
  • Aggravation of seizures: more with clozapine, olanzapine, and chlorpromazine; less with risperidone and quetiapine
  • Postural hypotension and inhibition of ejaculation: α-blocking property
  • Retinal degeneration: thioridazine
  • Agranulocytosis: clozapine
  • Cataract formation: quetiapine
  • Cholestatic jaundice: chlorpromazine
  • Anticholinergic effects: dry mouth, blurred vision, constipation, urinary retention; maximum with thioridazine
  • Hyperprolactinemia, amenorrhea, and galactorrhea: due to D2 blockade in the pituitary
  • Extrapyramidal Symptoms (EPS): acute muscular dystonia, Parkinsonism, akathisia, malignant neuroleptic syndrome, tardive dyskinesia

Other Uses:

  • Acute mania and bipolar disorder
  • Severe depression with psychotic features
  • Alcoholic hallucinosis
  • Gilles de la Tourette’s syndrome and Huntington’s disease

Key Points:

  1. Haloperidol and fluphenazine are potent typical antipsychotics, while risperidone is the most potent atypical antipsychotic.
  2. Clozapine, quetiapine, and aripiprazole have a negligible risk of extrapyramidal adverse effects.
  3. Chlorpromazine, thioridazine, and clozapine have the strongest anticholinergic activity.
  4. Fluphenazine (enanthate and decanoate) and haloperidol (decanoate) are long-acting injectable forms of typical antipsychotics, while risperidone and paliperidone are available in long-acting injectable form as atypical antipsychotics.
  5. Haloperidol is the most commonly used antipsychotic by intravenous route.
  6. Ziprasidone, aripiprazole, asenapine, and iloperidone have a negligible risk of causing metabolic adverse effects such as weight gain, hyperlipidemia, and new-onset diabetes mellitus.
  7. Asenapine, paliperidone, and ziprasidone have the greatest potential to prolong the QT interval.

Disclaimer: This article is for informational purposes only and should not be taken as medical advice. Always consult with a healthcare professional before making any decisions related to medication or treatment.

Oh hi there 👋

Sign up to receive awesome content in your inbox, every month.

We don’t spam! Read our privacy policy for more info.

Oh hi there 👋

Sign up to receive awesome content in your inbox every month.

We don’t spam! Read our privacy policy for more info.

Disclaimer: This article is for informational purposes only and does not constitute medical advice. Always seek the advice of a healthcare provider with any questions regarding a medical condition.



Please enter your comment!
Please enter your name here

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Continue in browser
To install tap Add to Home Screen
Add to Home Screen
Pharmacology Mentor
Get our web app. It won't take up space on your phone.
See this post in...
Pharmacology Mentor
Add Pharmacology Mentor to Home Screen

For an optimized experience on mobile, add Pharmacology Mentor shortcut to your mobile device's home screen

1) Press the share button on your browser's menu bar
2) Press 'Add to Home Screen'.
Pharmacology Mentor We would like to show you notifications for the latest news and updates.
Allow Notifications