Can Invega Be Given Intramuscularly?
Yes, Invega (paliperidone) is available as an intramuscular long-acting injectable formulation called paliperidone palmitate (Invega Sustenna®/Xeplion®), which is FDA-approved for monthly IM administration in the deltoid or gluteal muscle. 1, 2, 3
Available IM Formulation
- Paliperidone palmitate is formulated as a suspension of nanocrystals in an aqueous solution that requires no refrigeration or reconstitution prior to administration 4, 2
- The IM formulation provides therapeutic drug release for up to one month, making it a true long-acting injectable option 4, 3
- This is distinct from oral Invega (paliperidone extended-release tablets), which cannot be given intramuscularly 5
FDA-Approved Initiation Regimen
The recommended loading dose regimen is:
- Day 1: 150 mg eq (234 mg) administered in the deltoid muscle 2, 6
- Day 8: 100 mg eq (156 mg) administered in the deltoid muscle 2, 6
- This initiation schedule achieves therapeutic blood levels rapidly without requiring oral supplementation 2, 6
Maintenance Dosing
- Monthly maintenance doses range from 25-150 mg eq (recommended: 75 mg eq/117 mg) 6
- Maintenance injections can be administered in either the deltoid or gluteal muscle 3, 6
- Monthly doses may be given ±7 days from the scheduled date without clinically significant impact on plasma concentrations 6
Critical Injection Site Considerations
The deltoid and gluteal injection sites are NOT therapeutically equivalent and should not be used interchangeably during maintenance therapy 7:
- Pharmacokinetic studies demonstrate significant differences in elimination half-life, peak plasma concentration, and absorption rate depending on injection site 7
- These pharmacokinetic shifts suggest the sites are not bioequivalent 7
- Switching between injection sites or using the same dose at different sites may result in unforeseen consequences in patient outcomes 7
Needle Selection Based on Weight and Site
For deltoid injections:
For gluteal injections:
- All patients: Use 1.5-inch, 22-gauge needle 6
Clinical Efficacy Evidence
- Multiple 9-13 week placebo-controlled trials demonstrated significant improvements in PANSS total scores compared to placebo 3
- Clinical response onset occurs within 8 days when using the recommended 150 mg eq initial dose 3
- A 24-week maintenance trial showed significantly longer time to relapse compared to placebo, with the study terminated early due to favorable results 3
- Non-inferiority to long-acting injectable risperidone was demonstrated in 13-week trials 3
Special Populations
Renal impairment:
- Mild impairment (CrCl 50-80 mL/min): Dosage adjustment required 6
- Paliperidone undergoes limited hepatic metabolism, minimizing hepatic drug-drug interactions 5
Elderly patients:
- Same dosage as younger adults if renal function is normal 6
- Adjust dose if age-related decline in creatinine clearance is present 6
Hepatic impairment:
- No adjustment needed for mild-moderate impairment 6
- No data available for severe hepatic impairment 6
Common Pitfalls to Avoid
- Do not confuse oral paliperidone with the IM formulation - they are different products with different administration routes 2, 5
- Do not switch between deltoid and gluteal sites during maintenance without recognizing potential therapeutic non-equivalence 7
- Do not use intramuscular administration for oral Invega tablets - only the palmitate formulation is designed for IM use 2
- Do not administer initial loading doses in the gluteal muscle - both day 1 and day 8 doses must be given in the deltoid 6
Safety Profile
- Tolerability is generally acceptable with no new safety signals compared to oral paliperidone, except for injection site reactions 3
- Most common adverse events include extrapyramidal symptoms, tachycardia, and somnolence 5
- Modest QTc prolongation may occur but typically without clinical symptoms 5
- Serum prolactin elevations occur similar to risperidone 5