Timing of Long-Acting Injectable Antipsychotic Administration After a Missed Dose
Administer the missed long-acting injectable antipsychotic as soon as the missed dose is identified, without waiting for the next scheduled injection date. 1
Immediate Action Required
When a patient misses a scheduled long-acting injectable (LAI) antipsychotic dose, immediate clinical intervention is necessary to prevent relapse. 1 The primary advantage of LAIs is that missed doses are immediately apparent to the clinical team, providing a critical window for intervention before a crisis develops 1.
Key Principles for Missed LAI Doses
Administer the injection as soon as the missed dose is discovered - there is no benefit to waiting until the next scheduled date, as this only extends the period of subtherapeutic drug levels 2
The timing window is medication-specific based on the half-life and pharmacokinetic profile of each LAI formulation 1
For haloperidol decanoate: Given its 3-week half-life, there is typically a grace period of several days to 1-2 weeks before plasma levels drop significantly, but the injection should still be given promptly upon recognition 1
For risperidone long-acting injection: With a 3-6 day release profile, the window is narrower and requires more urgent administration within days of the missed dose 3
Clinical Decision Algorithm
Step 1: Assess Time Since Missed Dose
Less than 1 week late: Administer the injection immediately without dose adjustment 2
1-2 weeks late: Administer the injection immediately; consider whether oral supplementation is needed based on symptom status 1
More than 2 weeks late: May require oral antipsychotic bridging while reinitiating the LAI, particularly for shorter-acting formulations 1
Step 2: Monitor for Early Relapse Signs
Non-adherence is the single most powerful predictor of relapse, with relapse rates five times higher among those who discontinue medication 1
Early intervention is critical - the 2025 INTEGRATE guidelines emphasize acting early when treatment effectiveness is compromised 1
Watch for emerging positive symptoms, behavioral changes, or functional decline that may indicate impending relapse 1
Critical Caveats
Risk of Relapse Without Prompt Action
Relapse risk increases dramatically with medication discontinuation, and this is true for both first and subsequent relapses 1
The risk ratio for relapse with inadequate antipsychotic coverage can approach 1.93 compared to continuous treatment 3
Patients who are clinically stable have the most to lose from a relapse, particularly those in early phases of illness 1
Avoiding Double Dosing
Never administer a double dose of LAI to "catch up" - this contradicts general missed-dose principles and risks toxicity 2
The long half-lives of LAI formulations mean that some drug remains in the system even after a missed dose 4
Switching Considerations
If switching between antipsychotics during a missed dose scenario, use gradual cross-titration informed by half-life and receptor profiles 1
Avoid combining high-potency typical antipsychotics (like haloperidol) with atypical antipsychotics (like risperidone) simultaneously, as this increases risk of neuroleptic malignant syndrome through additive dopamine-2 receptor blockade 5
Practical Implementation
Contact the patient immediately when a missed injection is identified through clinic no-shows or appointment tracking 1
Schedule the injection as an urgent appointment rather than waiting for the next routine visit 1
Use this as an opportunity to address adherence barriers and reinforce the importance of maintaining the injection schedule 2
Consider whether the patient would benefit from more frequent contact or additional psychosocial support to prevent future missed doses 1