Uzedy Dosing for Patients on Oral Risperidone 2mg Twice Daily
For a patient taking oral risperidone 2mg twice daily (4mg/day total), the recommended Uzedy (risperidone long-acting injection) dose is 37.5mg administered intramuscularly every 2 weeks.
Dose Conversion Algorithm
The conversion follows a tiered approach based on total daily oral risperidone dose 1:
- Oral risperidone ≤3mg/day → Uzedy 25mg every 2 weeks
- Oral risperidone >3mg to ≤5mg/day → Uzedy 37.5mg every 2 weeks
- Oral risperidone >5mg/day → Uzedy 50mg every 2 weeks
Since your patient takes 4mg/day oral risperidone, this falls into the middle tier requiring 37.5mg of Uzedy every 2 weeks 1
Critical Timing Considerations
Continue oral risperidone supplementation for the first 3 weeks after the initial Uzedy injection, as significant release of risperidone from the microspheres does not begin until 3 weeks post-injection 2
Steady-state plasma concentrations are not reached until after the fourth injection (approximately 8 weeks), so clinical response should be assessed over this timeframe 2
Evidence Supporting This Dosing
A 48-week randomized pharmacokinetic study specifically tested equivalent switching doses and found that the original FDA conversion recommendations were too low 1
Patients receiving 25mg or 37.5mg every 2 weeks showed increased symptom scores, decreased serum metabolite concentrations, and increased relapse tendency when the oral dose exceeded the lower threshold for each tier 1
The adjusted conversion algorithm (oral 3-5mg/day → 37.5mg injection) demonstrated maintained efficacy with reduced side effects compared to continued oral therapy 1
Advantages of This Conversion
Long-acting risperidone causes less plasma drug concentration fluctuation than oral formulations, providing more stable therapeutic levels 2
Studies demonstrate reduced extrapyramidal symptoms (Simpson-Angus Scale scores, p=0.028), lower prolactin levels (p=0.046), and improved UKU Side Effect Rating Scale scores (p=0.048) compared to equivalent oral dosing 1
Common Pitfalls to Avoid
Do not use the original FDA conversion of 4-6mg oral → 37.5mg injection, as this range is too broad and led to treatment failures in the lower end 1
Do not discontinue oral supplementation before 3 weeks, as this will result in a therapeutic gap and potential symptom exacerbation 2
Do not assess treatment failure before 8 weeks (fourth injection), as steady-state has not been achieved 2
Monitor for injection site reactions, though the incidence of injection site pain is low (≤10%) 2