Long Acting Injectable Risperidone

Jun 22, 2024

Long Acting Injectable Risperidone

Introduction

Speaker: Dr. Sesh Badmat, Professor of Psychiatry, National Institute of Mental Health and Neurosciences, Bangalore

Topics Covered:

  • Pharmacokinetics
  • Side effects
  • Dosage
  • Administration
  • Recent research

Types of Long Acting Injectable Risperidone

  1. Intramuscular Injection (IM)

    • Technology: Microencapsulation in a biodegradable polymer (PLGA)
    • Release: Slow release through diffusion over 1 to 21 days
    • Dosage Frequency: Once every 2 weeks
    • Available Dosages: 12.5 mg, 25 mg, 37.5 mg, 50 mg

  2. Subcutaneous Injection (SC)

    • Technology: Suspended in a biodegradable polymer matrix
    • Release: Fusion and gel formation
    • Dosage Frequency: Once a month
    • Available Dosages: 90 mg, 120 mg (Not marketed in India)

Administration Guidelines

Intramuscular Injection (IM)

  • Initial Dosage: Start with 12.5 mg
  • Increment: After 1 month, increase to 25 mg
  • Further Increments: Increment should occur after every 2 dosages<br>25 mg → 37.5 mg → 50 mg
  • Concomitant Oral Medication: Required for the first 3-4 weeks
  • Conversion from Oral Dosage:
    • 2 mg oral → 12.5 mg IM
    • 4 mg oral → 25 mg IM
    • 6 mg oral → 37.5 mg IM
    • 8 mg oral → 50 mg IM

Subcutaneous Injection (SC)

  • Dosage:
    • 2 mg oral → 90 mg SC Monthly
    • 4 mg oral → 120 mg SC Monthly
  • Concomitant Oral Medication: Not required
  • Administration: Suitable for maintenance therapy, not initial stabilization

Switching to Paliperidone (Pipon)

  • Reasons for Switching: Lesser side effects, longer intervals between injections
  • Conversion:
    • 25 mg IM Risperidone (every 2 weeks) → 50 mg Pipon (monthly)
    • 37.5 mg IM Risperidone (every 2 weeks) → 75 mg Pipon (monthly)
    • 50 mg IM Risperidone (every 2 weeks) → 100 mg Pipon (monthly)

Side Effects

  • Common: Prolactin elevation, weight gain, parkinsonism, sedation, hypotension, akathisia
  • Rare: Neuroleptic malignant syndrome (NMS), injection site pain
  • Management: Some may require anti-cholinergic drugs on a case-by-case basis

Research Evidence

First Episode Psychosis

  • Reference: International Clinical Psychopharmacology, 2019
  • Key Findings:
    • Long-acting Risperidone showed significant advantage over oral anti-psychotics
    • Improved adherence, reduced relapse, and rehospitalization

Schizophrenia

  • Reference: Schizophrenia Research, 2022
  • Study Design: Multi-center, open-label extension
  • Key Findings:
    • Effective, safe, and well-tolerated long-term treatment for schizophrenia
    • Beneficial for patients requiring stable, long-term medication

Bipolar Disorder

  • Reference: CNS Drugs, 2019
  • Key Findings:
    • Second-generation long-acting anti-psychotics (Risperidone and Aripiprazole) found effective
    • Especially useful for patients with rapid cycling or poor adherence to oral medication

Conclusion

  • Key Recommendations:
    • IM Injection: Requires concomitant oral medication for the first 3-4 weeks
    • SC Injection: Does not require concomitant oral medication
    • Dosage Adjustment: Should occur monthly after every 2 doses
  • Final Note: Long-acting Risperidone is effective for both schizophrenia and bipolar disorder, with proper administration improving patient outcomes.