Peak Plasma Concentration After Invega Injection
Peak plasma concentration (Cmax) occurs approximately 13 days after intramuscular injection of Invega (paliperidone palmitate) long-acting injectable. 1
Pharmacokinetic Timeline
The absorption profile of paliperidone palmitate follows a distinct pattern after intramuscular administration:
- Drug release begins: Day 1 (immediately after injection)
- Peak concentration (Cmax): Day 13 (approximately 2 weeks post-injection)
- Duration of release: Up to 126 days 1
For the oral extended-release formulation (Invega tablets), the timeline is markedly different, with peak concentration occurring at approximately 24 hours after a single oral dose 2.
Important Clinical Considerations
Injection Site Matters
Deltoid injections produce approximately 28% higher peak concentrations compared to gluteal injections 2. This pharmacokinetic difference is clinically significant:
- Initial loading doses (day 1 and day 8) must be administered in the deltoid muscle to achieve therapeutic concentrations rapidly
- Maintenance doses can be given in either deltoid or gluteal muscle, but these sites are not therapeutically equivalent and should not be switched arbitrarily 3
Steady-State Achievement
- Steady-state concentrations are attained within 4-5 days of dosing in most patients 2
- The mean steady-state peak:trough ratio is 1.7 (range 1.2-3.1) for a 9 mg oral dose 2
Common Pitfall to Avoid
Do not assume deltoid and gluteal injections are interchangeable for maintenance dosing. While both sites are approved, switching between sites may result in unforeseen shifts in plasma concentrations that could affect clinical outcomes 3. If you must switch injection sites, monitor the patient more closely for changes in efficacy or tolerability.
The terminal elimination half-life is approximately 23 hours for the oral formulation 2, though the long-acting injectable formulation demonstrates sustained release over months due to its depot characteristics.