Glucose dysregulation among veterans living with schizophrenia-related disorders after switching second-generation antipsychotics

Systematic Literature Review of the Methods Used to Compare Newer Second-Generation Agents for the Management of Schizophrenia: A focus on Health Technology Assessment

BACKGROUND

The challenges of comparative effectiveness to support health technology assessment (HTA) agencies are important considerations in the choices of antipsychotic medications for the treatment of schizophrenia.

OBJECTIVES

Our aim was to assess the study methods used and outcomes reported in the published literature to address the question of comparative effectiveness of newer antipsychotic agents and the adequacy and availability of evidence to support HTA agencies.

DATA SOURCE

A systematic search of the PubMed database from 1 January 2009 to 30 September 2013 was conducted to identify studies evaluating new atypical antipsychotics reporting on comparative effectiveness.

STUDY SELECTION

The systematic review comprised of studies on schizophrenia patients where at least two drugs were being compared and at least one treatment group received one of the following second-generation antipsychotics: risperidone, olanzapine, aripiprazole, paliperidone, asenapine, iloperidone, lurasidone, and quetiapine. The included studies were also required to have an efficacy, safety or economic outcome, such as Positive and Negative Syndrome Scale (PANSS) score, weight gain, resource utilization, or costs.

STUDY APPRAISAL AND SYNTHESIS METHODS

Two reviewers (BW and GK) independently applied the inclusion criteria. Disagreements between reviewers were resolved by consensus, referring to the original sources. Information on the methodology and outcomes was collected for each included study. This included study description, head-to-head drug comparison, patient population, study methodology, statistical methods, reported outcomes, study support, and journal type.

RESULTS

A total of 198 studies were identified from electronic search methods. The largest category of studies was randomized controlled trials [RCTs] (N = 73; 36.9%), which were largely directed at the regulatory endpoint. Fewer studies were undertaken for HTA-purposes cohort studies (N = 53; 26.8%), meta-analyses (N = 32; 16.2%), economic studies (N = 14; 7.1%), and cross-sectional studies (N = 13; 6.6%). Direct head-to-head comparisons preferred by HTA were dominated by the comparison involving olanzapine and risperidone, representing 149 (75.3%) and 119 (60.1%) studies, respectively. RCTs, which are the primary study type for regulatory submissions, showed a lack of bias. Studies aimed at HTA were not as well performed. Cohort studies suffered from bias in the selection of comparison groups, lack of control for confounders, and differential dropout rates. As a group, cross-sectional studies scored poorly for bias, with a primary failure to identify a representative sample. Economic studies showed highly variable bias, with bias in the representation of effectiveness data, model assumptions without validation, and lack of sensitivity analyses.

LIMITATIONS

One limitation of this systematic review is that it only included studies from 2009 to 2013, potentially excluding some earlier comparator studies, particularly those involving first-generation antipsychotics.

CONCLUSIONS

This review of comparative effectiveness studies of second-generation antipsychotic agents for schizophrenic patients revealed a wide range of study types, study methodologies, and outcomes. For traditional efficacy outcomes and select safety outcomes, there is strong evidence from many well-conducted studies; however, there are fewer studies of types preferred by HTA with limited head-to-head comparisons and a higher risk of bias in the execution of these studies.

Management of antipsychotic-related weight gain

Despite variations across individuals and agents, antipsychotics are associated with clearly documented weight gain and adverse metabolic effects. Although increased appetite/caloric intake and various receptors, hormones and peptides have been implicated, biological mechanisms contributing to the increase in weight and glucose and lipid abnormalities with antipsychotics are largely unknown. This has hampered the creation of antipsychotics that are free of cardiometabolic effects, even in antipsychotic-naive/early-phase patients, as well as the development of strategies that can prevent or drastically diminish the adverse cardiometabolic effects. In general, three strategies can reduce the cardiometabolic risk of antipsychotics: switching to a less orexigenic/metabolically adverse antipsychotic; adjunctive behavioral treatments; and adjunctive pharmacologic interventions. However, each of these strategies has only been shown to be modestly effective. Among different behavioral interventions (N = 14, n = 746), group and individual treatment, dietary counseling and cognitive-behavioral therapy seem to be similarly effective. Among 15 different pharmacologic strategies (N = 35, n = 1629), only metformin, fenfluramine, sibutramine, topiramate and reboxetine were more effective than placebo, with the most evidence being available for metformin, and no head-to-head trials comparing individual pharmacologic interventions. However, even in the most successful trials the risk reduction was modest. Weight was not decreased to a pretreatment level, and despite superiority compared with placebo, weight gain still often occurred, particularly in antipsychotic-naive patients and when interventions were 'preventively' coinitiated with antipsychotics. Future research should focus on combining treatment modalities or agents and on exploring novel mechanism-based interventions.