Paliperidone Intramuscular Injection Dosing Regimen
The recommended dosing regimen for Invega (paliperidone) intramuscular injections is an initiation dose of 150 mg eq (234 mg) on day 1 followed by 100 mg eq (156 mg) on day 8, both administered in the deltoid muscle, then monthly maintenance doses of 25-150 mg eq (39-234 mg) with a recommended dose of 75 mg eq (117 mg) administered in either the deltoid or gluteal muscle.
Initial Dosing Protocol
The initiation regimen for paliperidone palmitate (Invega) consists of two loading doses:
- Day 1: 150 mg equivalent (234 mg) administered in the deltoid muscle
- Day 8: 100 mg equivalent (156 mg) administered in the deltoid muscle
This two-dose initiation regimen achieves therapeutic blood levels rapidly without requiring oral supplementation 1. The deltoid muscle is specifically recommended for these initial doses because it provides higher and faster absorption compared to gluteal administration.
Needle Selection for Initial Doses
- For patients <90 kg: Use a 1-inch 23-gauge needle
- For patients ≥90 kg: Use a 1.5-inch 22-gauge needle
Maintenance Dosing
After the initiation regimen, monthly maintenance doses should be administered:
- Dose range: 25-150 mg equivalent (39-234 mg)
- Recommended dose: 75 mg equivalent (117 mg)
- Administration site: Either deltoid or gluteal muscle
- Timing flexibility: Monthly doses can be administered ±7 days without clinically significant impact on plasma concentrations
Needle Selection for Maintenance Doses
- For deltoid injections:
- Patients <90 kg: 1-inch 23-gauge needle
- Patients ≥90 kg: 1.5-inch 22-gauge needle
- For gluteal injections: 1.5-inch 22-gauge needle regardless of weight
Site Selection Considerations
Pharmacokinetic studies have shown differences between deltoid and gluteal administration:
- Deltoid injections result in approximately 20-30% higher drug exposure compared to gluteal injections 2
- Deltoid injections show higher fluctuation index with greater interpatient variability (75.9%) compared to gluteal injections (58.5%) 2
- Gluteal injections demonstrate better local site tolerability 2
Special Populations
Renal Impairment
- Mild impairment (CrCl 50-80 mL/min): Dosage adjustment required
- No specific dose adjustments are mentioned for moderate to severe impairment, but caution is advised
Hepatic Impairment
- Mild to moderate impairment: No dose adjustment required
- Severe impairment: Insufficient data available
Elderly Patients
- With normal renal function: Same dosage as younger adults
- With age-related decline in renal function: Adjust dosage accordingly
Missed Doses
If the day 8 dose is missed:
- If <4 days have passed: Administer the second dose as soon as possible
- If >4 days have passed: Re-initiation may be necessary
For maintenance doses:
- If missed by <4 weeks: Administer the dose as soon as possible
- If missed by >4 weeks but <6 weeks: Continue with the next scheduled dose
- If missed by >6 weeks: Re-initiation schedule is required based on time since last injection
Switching from Other Antipsychotics
- From oral antipsychotics: Paliperidone palmitate can be initiated the day after discontinuing previous oral treatment
- From other long-acting injectables: Initiate paliperidone palmitate at the time of the next scheduled injection of the previous LAI
The dosing recommendations for paliperidone palmitate are based on extensive population pharmacokinetic modeling and clinical trial data that demonstrate its efficacy in controlling acute symptoms of schizophrenia and delaying time to relapse 3, 1.