What oral risperidone dose is equivalent to a 25 mg intramuscular injection of Risperidone Microspheres (Risperdal Consta) administered every 14 days?

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Oral Risperidone Equivalent for 25 mg IM Injection Every 2 Weeks

For a patient receiving risperidone long-acting injection 25 mg every 14 days, the equivalent oral dose is 3 mg/day or less. 1, 2

FDA-Approved Conversion Guidelines

The FDA label for risperidone extended-release injectable suspension does not provide a direct conversion table, but clinical trial data establish the relationship between oral and injectable formulations. 1

  • Patients on oral risperidone ≤3 mg/day should receive 25 mg IM every 2 weeks 2
  • Patients on oral risperidone >3 mg/day but ≤5 mg/day should receive 37.5 mg IM every 2 weeks 2
  • Patients on oral risperidone >5 mg/day should receive 50 mg IM every 2 weeks 2

Pharmacokinetic Considerations

Working backward from these conversion ratios, a patient receiving 25 mg IM every 2 weeks is receiving the equivalent of approximately 2–3 mg/day oral risperidone. 2

  • The long-acting formulation provides steady-state plasma concentrations after the fourth injection (approximately 8 weeks), with significant release beginning 3 weeks after the first injection 1, 3
  • Plasma active moiety (risperidone plus 9-hydroxyrisperidone) levels at steady state are bioequivalent between the 25 mg IM formulation and corresponding oral doses 4
  • The injectable formulation causes less plasma concentration fluctuation than oral dosing, which may improve tolerability 3

Critical Conversion Pitfalls

If converting FROM 25 mg IM TO oral risperidone:

  • Start oral risperidone 2–3 mg/day immediately when discontinuing the injection 2
  • The last injection will continue releasing drug for 7–8 weeks after administration, so overlap is not necessary 1, 3
  • Monitor for symptom recurrence during the transition period, as elimination is gradual 4

If converting FROM oral TO 25 mg IM:

  • Continue oral risperidone (or another antipsychotic) for 3 weeks after the first injection to maintain therapeutic levels until the main release phase begins 1
  • The 25 mg IM dose is appropriate for patients previously stable on oral risperidone ≤3 mg/day 2

Special Population Adjustments

  • Elderly patients: The recommended dose is 25 mg IM every 2 weeks with 3-week oral supplementation after the first injection 1
  • Renal or hepatic impairment: Patients should tolerate oral risperidone 2 mg/day before initiating 25 mg IM; alternatively, consider starting at 12.5 mg IM (though efficacy at this dose is not established) 1

Monitoring During Conversion

  • Extrapyramidal symptoms (EPS) can occur even at low doses equivalent to 2 mg/day oral risperidone 5
  • The long-acting formulation demonstrated reduced EPS compared to equivalent oral doses in clinical trials, with lower Simpson-Angus Scale scores and reduced prolactin levels 2
  • Assess for symptom control at 4-week intervals, as upward dose adjustments should not occur more frequently than every 4 weeks 1

References

5
Guideline

Risperidone Treatment Guidelines

Praxis Medical Insights: Practical Summaries of Clinical Guidelines, 2026

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Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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