Switching from Invega Trinza 819mg to Sustenna 234mg
When switching from Invega Trinza 819mg to Sustenna 234mg, administer Sustenna 234mg exactly 3 months after the last Trinza dose, then continue monthly Sustenna injections thereafter—no loading doses are required. 1
Direct Conversion Protocol
The FDA-approved switching regimen is straightforward and based on a 3.5-fold dose reduction:
- Last Trinza dose: 819mg
- First Sustenna dose: 234mg (administered 3 months after the last Trinza injection)
- Subsequent doses: Continue Sustenna 234mg every month
This conversion maintains therapeutic paliperidone exposure without requiring the standard Sustenna initiation protocol (which normally involves loading doses on days 1 and 8). 1
Key Implementation Points
Timing
- Administer the first Sustenna dose exactly when the next Trinza dose would have been due (3 months after the last Trinza injection)
- The transition can occur up to 2 weeks before or after the 3-month timepoint if scheduling flexibility is needed 1
Injection Site
- Either deltoid or gluteal muscle is acceptable for the first Sustenna dose
- For deltoid injections: use 1-inch needle if patient <90kg, 1.5-inch if ≥90kg
- For gluteal injections: use 1.5-inch needle regardless of weight 1
No Overlap Period Required
Unlike switching between different antipsychotic classes, no cross-titration or overlap is needed here since both formulations contain the same active moiety (paliperidone palmitate). The pharmacokinetic modeling demonstrates that the 3-month interval provides appropriate plasma level continuity. 2
Clinical Monitoring Considerations
Watch for symptom breakthrough during weeks 8-12 after the last Trinza dose, as this represents the transition period when Trinza levels are declining and Sustenna hasn't yet reached steady state. While the FDA protocol doesn't mandate oral supplementation, consider having oral paliperidone available if early warning signs emerge.
The gradual cross-titration principle mentioned in recent schizophrenia guidelines 3 applies when switching between different antipsychotic compounds, but the same-drug formulation switch from Trinza to Sustenna follows the manufacturer's direct conversion table without gradual titration.
Common Pitfalls to Avoid
- Do not use Sustenna loading doses (234mg day 1, 156mg day 8)—this is only for antipsychotic-naive patients or those switching from oral medications
- Do not administer Sustenna earlier than 2.5 months after the last Trinza dose, as this risks excessive plasma levels
- Do not delay beyond 4 months without implementing the missed-dose protocol, which would require restarting with two weekly Sustenna doses 1