Antipsychotic agents are the mainstay of treatment for patients with schizophrenia,1-3 and when taken regularly, they can greatly improve patient outcomes. Unfortunately, many studies have documented poor adherence to antipsychotic regimens in patients with schizophrenia, which often leads to an exacerbation of symptoms and preventable hospitalizations.4-8 In order to improve adherence, many clinicians prescribe long-acting injectable antipsychotics (LAIAs).
LAIAs help improve adherence, but these benefits are seen only in patients who receive their injections within a specific time frame.9-11 LAIAs administered outside of this time frame (missed doses) can lead to reoccurrence or exacerbation of symptoms. This article explains how to adequately manage missed LAIA doses.
First-generation long-acting injectable antipsychotics
Two first-generation antipsychotics are available as a long-acting injectable formulation: haloperidol decanoate and fluphenazine decanoate. Due to the increased risk of extrapyramidal symptoms, use of these agents have decreased, and they are often less preferred than second-generation LAIAs. Furthermore, unlike many of the newer second-generation LAIAs, first-generation LAIAs lack literature on how to manage missed doses. Therefore, clinicians should analyze the pharmacokinetic properties of these agents (Table 112-28), as well as the patient’s medical history and clinical presentation, in order to determine how best to address missed doses.
Haloperidol decanoate plasma concentrations peak approximately 6 days after the injection.12 The medication has a half-life of 3 weeks. One study found that haloperidol plasma concentrations were detectable 13 weeks after the discontinuation of haloperidol decanoate.17 This same study also found that the change in plasma levels from 3 to 6 weeks after the last dose was minimal.17 Based on these findings, Figure 1 summarizes our recommendations for addressing missed haloperidol decanoate doses.
Fluphenazine decanoate levels peak 24 hours after the injection.18 An estimated therapeutic range for fluphenazine is 0.2 to 2 ng/mL.21-25 One study that evaluated fluphenazine decanoate levels following discontinuation after reaching steady state found there was no significant difference in plasma levels 6 weeks after the last dose of fluphenazine, but a significant decrease in levels 8 to 12 weeks after the last dose.26 Other studies found that fluphenazine levels were detectable 21 to 24 weeks following fluphenazine decanoate discontinuation.27,28 Based on these findings, Figure 2 summarizes our recommendations for addressing missed fluphenazine decanoate doses.
Continue to: Second-generation LAIAs