Typical antipsychotics

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Typical antipsychotics

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A 50-year-old man comes to the office because of vision changes over the last several months. The patient was diagnosed with schizophrenia at the age of 40. His condition has been well managed with medications, which he has been taking for the last 10 years. The patient lives in a group home and according to his caretaker, prefers to stay alone but is not disruptive. Additional past medical history is significant for erectile dysfunction and latent tuberculosis. The patient also had a urinary tract infection 6 months ago that was treated with antibiotics. Temperature is 37.2°C (99.0°F), pulse is 102/min, respirations are 18/min, and blood pressure is 130/90 mmHg. Ophthalmologic examination shows opacities on the bilateral cornea. No retinal pigmentation is seen. Which of the following medications is the most likely cause of this patient’s presentation?  

External References

First Aid

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2023

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2021

Chlorpromazine p. 591

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Antipsychotics, as their name implies, are mainly used to treat schizophrenia and other psychotic conditions. Even though the exact cause of schizophrenia is still unknown, there's some evidence that suggests it’s related to altered levels of the neurotransmitter dopamine. Now, antipsychotics are subdivided into two main categories: the first generation or typical antipsychotics, and the second generation or atypical antipsychotics.

Alright, within the brain, dopamine is found in 4 main dopamine pathways: the mesolimbic pathway, which controls motivation and desire; the mesocortical pathway, which helps regulate emotions; the nigrostriatal pathway, which contains motor neurons that bypass the medullary pyramids, to control involuntary movements and coordination; and lastly, the tuberoinfundibular pathway, which releases dopamine to limit the secretion of prolactin. Other regions of the central nervous system that are rich in dopamine receptors include the chemoreceptor trigger zone, which initiates the vomiting reflex, and the medullary periventricular pathway, which regulates eating behavior.

However, in schizophrenia, altered levels of dopamine mainly affect the mesolimbic pathway and mesocortical pathway. There’s usually high levels of dopamine in the mesolimbic pathway which cause positive symptoms of schizophrenia, such as delusions, hallucinations, and disorganized thought. On the other hand, low levels of dopamine in the mesocortical pathway cause negative symptoms of schizophrenia, such as lack of motivation, social withdrawal, and “flat affect,” which basically means a lack of emotions.

When it comes to treating schizophrenia, some typical antipsychotics like haloperidol, trifluoperazine, and fluphenazine have a higher potency, which means you need less of it to achieve a therapeutic effect. The lower potency antipsychotics include thioridazine and chlorpromazine and they require larger doses to achieve the same therapeutic effect as high-potency antipsychotics.

Summary

Typical antipsychotics, also known as first-generation antipsychotics, are a class of medications used to treat various psychiatric disorders, particularly schizophrenia and other psychotic disorders. They work by blocking dopamine D2 receptors in the mesolimbic pathway in the brain, which helps to reduce the symptoms of psychosis.

Typical antipsychotics include medications such as chlorpromazine, haloperidol, and fluphenazine. These medications are generally effective at reducing positive symptoms of psychosis, such as hallucinations and delusions, but may have limited effectiveness for negative symptoms and may also cause significant side effects.

Common side effects of typical antipsychotics include extrapyramidal symptoms, such as tremors and muscle rigidity, as well as weight gain, sedation, and sexual dysfunction. Long-term use of these medications may also be associated with a higher risk of developing tardive dyskinesia, a movement disorder characterized by involuntary muscle movements.

Sources

  1. "Katzung & Trevor's Pharmacology Examination and Board Review,12th Edition" McGraw-Hill Education / Medical (2018)
  2. "Rang and Dale's Pharmacology" Elsevier (2019)
  3. "Goodman and Gilman's The Pharmacological Basis of Therapeutics, 13th Edition" McGraw-Hill Education / Medical (2017)
  4. "Neuroleptic Malignant Syndrome" Annals of Pharmacotherapy (2016)
  5. "Second-generation versus first-generation antipsychotic drugs for schizophrenia: a meta-analysis" The Lancet (2009)
  6. "Update on Typical and Atypical Antipsychotic Drugs" Annual Review of Medicine (2013)
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