Objective: As psychopathology and social functioning can worsen with repeated psychotic episodes in schizophrenia, relapse prevention is critical. Because high nonadherence rates limit the efficacy of pharmacotherapy, the use of long-acting injectable (LAI) antipsychotics is considered an important treatment option. To date, many studies comparing LAIs and oral antipsychotics have been conducted; however, the results are mixed, and careful interpretation of the data is required. Study Design and Setting: Selective review of existing literature regarding LAIs. We especially focused the discussion on the impact of the design of studies with different approaches comparing LAIs and oral antipsychotics in preventing relapse. Result: The results were diverse and were influenced by the design used, that is, randomized controlled trials (RCTs) showed LAIs and oral antipsychotics to have similar effects, whereas mirror-image and some large cohort studies showed LAIs to be superior to oral antipsychotics. Conclusion: Divergent results from studies using different methodologies create a dilemma for comparative effectiveness research, and LAI studies may serve as an example of a situation in which a conventional RCT is not the gold standard. Traditional RCTs generally increase adherence compared with clinical practice and, therefore, might not be well suited to detect differences between LAIs and oral medications, because any increase in adherence affects patients on oral medications more than those on LAIs and thus leads to an underestimation of any potential difference in effectiveness. A possible solution would be the implementation of a true effectiveness trial in which post-randomization involvement would be kept to a minimum to better reflect routine practice.
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