Cost-effectiveness simulation analysis of schizophrenia at the Instituto Mexicano del Seguro Social: Assessment of typical and atypical antipsychotics

Systematic review of the methods of health economic models assessing antipsychotic medication for schizophrenia

BACKGROUND

Numerous economic models have assessed the cost-effectiveness of antipsychotic medications in schizophrenia. It is important to understand what key impacts of antipsychotic medications were considered in the existing models and limitations of existing models in order to inform the development of future models.

OBJECTIVES

This systematic review aims to identify which clinical benefits, clinical harms, costs and cost savings of antipsychotic medication have been considered by existing models, to assess quality of existing models and to suggest good practice recommendations for future economic models of antipsychotic medications.

METHODS

An electronic search was performed on multiple databases (MEDLINE, EMBASE, PsycInfo, Cochrane database of systematic reviews, The NHS Economic Evaluation Database and Health Technology Assessment database) to identify economic models of schizophrenia published between 2005-2020. Two independent reviewers selected studies for inclusion. Study quality was assessed using the National Institute for Health and Care Excellence (NICE) checklist and the Cooper hierarchy. Key impacts of antipsychotic medications considered by exiting models were descriptively summarised.

RESULTS

Sixty models were included. Existing models varied greatly in key impacts of antipsychotic medication included in the model, especially in clinical outcomes used for assessing reduction in psychotic symptoms and types of adverse events considered in the model. Quality of existing models was generally low due to failure to capture the health and cost impact of adverse events of antipsychotic medications and input data not obtained from best available source. Good practices for modelling antipsychotic medications are suggested.

DISCUSSIONS

This review highlights inconsistency in key impacts considered by different models, and limitations of the existing models. Recommendations on future research are provided.

Trifluoperazine versus placebo for schizophrenia

BACKGROUND

Trifluoperazine is a long-established high potency typical antipsychotic drug used in the treatment of schizophrenia and schizophrenia-like illnesses.

OBJECTIVES

To determine absolute effects of trifluoperazine for schizophrenia and schizophrenia-like illnesses compared with placebo.To critically appraise and summarise current evidence on the resource use, cost and economic evaluation of trifluoperazine compared with placebo for schizophrenia.

SEARCH METHODS

Searches of the Cochrane Schizophrenia Group's register of trials (July 2012), supplemented with handsearching, reference searching, personal communication and contact with industry. Two review authors undertook a search for economic studies using the Cochrane Schizophrenia Group's Health Economic Database (CSzGHED) on the 9th April 2013.

SELECTION CRITERIA

All available clinical randomised trials involving people with schizophrenia and schizophrenia-like illnesses that compare trifluoperazine with placebo.

DATA COLLECTION AND ANALYSIS

Studies for the effects of interventions were reliably selected by a review team and data were doubly independently extracted to reduce bias. We only used dichotomous data, using intention-to-treat analysis when possible. Data were estimated using risk ratio (RR) with 95% confidence intervals (CI). A 'Summary of findings' table was produced, where possible, for each primary outcome using GRADE. Economic studies were searched and reliably selected by review authors (VF and SS) to provide an economic summary of available data. Where no relevant economic studies were eligible for inclusion, the economic review team valued the already-included effectiveness outcome data to provide a rudimentary economic summary.

MAIN RESULTS

This review included 10 studies with a total number of 686 participants featuring in 20 different outcomes of interest. Overall, there was significant clinical improvement in clinical global state at medium term amongst people receiving trifluoperazine (3 RCTs, n = 417, RR 4.61, CI 1.54 to 13.84, low quality evidence) and significantly fewer people receiving trifluoperazine left the studies early due to relapse or worsening at medium term (2 RCTs, n = 381, RR 0.34, CI 0.23 to 0.49, low quality evidence). However, results were equivocal for leaving the study early at medium term for any reason (2 RCTs, n = 391, RR 0.80, CI 0.17 to 3.81, very low quality evidence) and due to severe adverse effects (2 RCTs, n = 391, RR 1.54, CI 0.56 to 4.24, very low quality evidence). Equivocal data were also found for intensified symptoms at medium term (2 RCTs, n = 80, RR 1.05, CI 0.54 to 2.05, very low quality evidence) and rates of agitation or distress again at medium term (1 RCT, n = 52, RR 2.00, CI 0.19 to 20.72, very low quality evidence). Comparison between low and high-dose trifluoperazine with placebo from a single study provided equivocal evidence of effects. For economic outcomes, we valued outcomes in GBP terms and presented them in additional tables; there was an estimated saving of £3488.3 in favour of trifluoperazine. However, numerous assumptions were made and these savings need to be interpreted in light of those assumptions.

AUTHORS' CONCLUSIONS

Our results agree with existing evidence that compared to placebo, trifluoperazine is an effective antipsychotic for people with schizophrenia. Furthermore, our review provides supportive evidence that trifluoperazine increases the risk of extrapyramidal adverse effects. Although the effect sizes against placebo are similar to those observed with other agents, they are based on data from many small, pre-CONSORT trials with generally either a low or very low GRADE evidence that has limited implication for clinical practice. Large, independent trials are needed that adhere to the CONSORT statement to compare trifluoperazine with placebo used in the treatment of schizophrenia and schizophrenia-like illnesses.