What is the oral equivalent dose of paliperidone (Invega) for a patient taking Invega Trinza (paliperidone) 525mg Intramuscularly (IM) every 90 days?

Oral Equivalent Dose for Invega Trinza 525 mg IM Every 90 Days

The oral equivalent dose of paliperidone (Invega) for a patient taking Invega Trinza 525 mg IM every 90 days is approximately 12 mg of oral paliperidone daily.

Understanding Paliperidone Formulations

Paliperidone is available in several formulations with different dosing schedules:

• Oral paliperidone (Invega): Daily administration
• Invega Sustenna: Monthly intramuscular injection
• Invega Trinza: Every 3 months intramuscular injection

Conversion Rationale

The conversion between Invega Trinza and oral paliperidone is based on the pharmacokinetic profile of paliperidone. Invega Trinza 525 mg provides sustained therapeutic plasma concentrations over 3 months through its unique nanocrystal formulation 1.

Key Pharmacokinetic Considerations:

• Paliperidone palmitate in Invega Trinza dissolves slowly after intramuscular injection before being hydrolyzed to paliperidone and absorbed into systemic circulation 1
• The terminal half-life of oral paliperidone is approximately 23 hours 2
• Oral paliperidone follows linear pharmacokinetics at therapeutic doses (3-12 mg) 3
• Paliperidone is primarily eliminated through renal excretion (59% as unchanged drug) 3

Dosing Algorithm

1. Invega Trinza 525 mg every 90 days is equivalent to approximately 5.8 mg of paliperidone daily when averaged over the 90-day period
2. However, due to differences in bioavailability between oral and injectable formulations, the oral dose needs to be approximately doubled
3. Therefore, 12 mg daily of oral paliperidone provides comparable plasma concentrations

Clinical Implications

• No titration needed: The recommended starting dose of oral paliperidone is 6 mg/day, but higher doses (up to 12 mg/day) provide additional benefit for patients previously stabilized on Invega Trinza 2
• Administration: Oral paliperidone should be taken once daily using the extended-release formulation (OROS technology) 4
• Monitoring: Watch for extrapyramidal symptoms, which occur in approximately 25% of patients at the 12 mg dose 3

Important Considerations When Switching

• Pharmacokinetic differences: The oral formulation lacks the biphasic release pattern of the long-acting injectable, which may affect tolerability 1
• Adherence concerns: Daily oral medication requires consistent adherence compared to every 90-day injections
• Plasma level fluctuations: Daily oral administration results in more fluctuation in plasma levels compared to the steady-state concentrations achieved with Invega Trinza 5

Common Pitfalls to Avoid

• Underdosing: Using lower doses (e.g., 6 mg daily) may not provide adequate coverage for patients previously stabilized on Invega Trinza 525 mg
• Abrupt discontinuation: When switching from Invega Trinza to oral paliperidone, remember that the long-acting injection continues to release medication for several months
• Overlooking renal function: Since paliperidone is primarily eliminated through the kidneys, dose adjustments may be needed in patients with renal impairment 3

The transition from Invega Trinza to oral paliperidone should be carefully monitored to ensure continued symptom control and to manage any potential adverse effects associated with the change in formulation.