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Related Experiment Videos

A PET study evaluating dopamine D2 receptor occupancy for long-acting injectable risperidone.

Gary Remington1, David Mamo, Alain Labelle

  • 1Schizophrenia Program, Centre for Addiction and Mental Health, Toronto, Ont. M5T 1R8, Canada. gary_remington@camh.net

The American Journal of Psychiatry
|March 4, 2006
PubMed
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Long-acting injectable risperidone effectively targets dopamine D(2) receptors in schizophrenia patients. Doses of 25 or 50 mg are recommended to balance efficacy and minimize side effects.

Area of Science:

  • Neuroscience
  • Psychopharmacology

Background:

  • Long-acting injectable risperidone is the first available depot atypical antipsychotic.
  • Understanding its dopamine D(2) receptor binding is crucial for optimizing treatment.

Purpose of the Study:

  • To evaluate the dopamine D(2) receptor occupancy of injectable risperidone at 25, 50, and 75 mg doses.
  • To determine the relationship between dosage, plasma concentrations, and D(2) occupancy.

Main Methods:

  • Positron emission tomography (PET) with [(11)C]raclopride was used to measure D(2) occupancy in nine schizophrenia patients.
  • D(2) occupancy was assessed twice during the 2-week injection interval (post- and pre-injection).
  • Plasma levels of risperidone and 9-hydroxyrisperidone were measured concurrently.

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Main Results:

  • All tested doses achieved peak D(2) occupancy above the 65% threshold for clinical response.
  • The 75-mg dose approached the 80% threshold associated with extrapyramidal symptoms.
  • A significant dose-dependent correlation was observed between plasma concentrations and D(2) occupancy.

Conclusions:

  • Injectable risperidone demonstrates significant D(2) receptor engagement at therapeutic doses.
  • Doses of 25 or 50 mg appear optimal for balancing clinical efficacy and minimizing extrapyramidal symptom risk.
  • Further research may refine dosing strategies for long-acting risperidone therapy.