Health Technology Assessment (Oct 2023)
A pragmatic, multicentre, double-blind, placebo-controlled randomised trial to assess the safety, clinical and cost-effectiveness of mirtazapine and carbamazepine in people with Alzheimer’s disease and agitated behaviours: the HTA-SYMBAD trial
Abstract
Background Agitation is common and impacts negatively on people with dementia and carers. Non-drug patient-centred care is first-line treatment, but we need other treatment when this fails. Current evidence is sparse on safer and effective alternatives to antipsychotics. Objectives To assess clinical and cost-effectiveness and safety of mirtazapine and carbamazepine in treating agitation in dementia. Design Pragmatic, phase III, multicentre, double-blind, superiority, randomised, placebo-controlled trial of the clinical effectiveness of mirtazapine over 12 weeks (carbamazepine arm discontinued). Setting Twenty-six UK secondary care centres. Participants Eligibility: probable or possible Alzheimer’s disease, agitation unresponsive to non-drug treatment, Cohen-Mansfield Agitation Inventory score ≥ 45. Interventions Mirtazapine (target 45 mg), carbamazepine (target 300 mg) and placebo. Outcome measures Primary: Cohen-Mansfield Agitation Inventory score 12 weeks post randomisation. Main economic outcome evaluation: incremental cost per six-point difference in Cohen-Mansfield Agitation Inventory score at 12 weeks, from health and social care system perspective. Data from participants and informants at baseline, 6 and 12 weeks. Long-term follow-up Cohen-Mansfield Agitation Inventory data collected by telephone from informants at 6 and 12 months. Randomisation and blinding Participants allocated 1 : 1 : 1 ratio (to discontinuation of the carbamazepine arm, 1 : 1 thereafter) to receive placebo or carbamazepine or mirtazapine, with treatment as usual. Random allocation was block stratified by centre and residence type with random block lengths of three or six (after discontinuation of carbamazepine, two or four). Double-blind, with drug and placebo identically encapsulated. Referring clinicians, participants, trial management team and research workers who did assessments were masked to group allocation. Results Two hundred and forty-four participants recruited and randomised (102 mirtazapine, 102 placebo, 40 carbamazepine). The carbamazepine arm was discontinued due to slow overall recruitment; carbamazepine/placebo analyses are therefore statistically underpowered and not detailed in the abstract. Mean difference placebo-mirtazapine (−1.74, 95% confidence interval −7.17 to 3.69; p = 0.53). Harms: The number of controls with adverse events (65/102, 64%) was similar to the mirtazapine group (67/102, 66%). However, there were more deaths in the mirtazapine group (n = 7) by week 16 than in the control group (n = 1). Post hoc analysis suggests this was of marginal statistical significance (p = 0.065); this difference did not persist at 6- and 12-month assessments. At 12 weeks, the costs of unpaid care by the dyadic carer were significantly higher in the mirtazapine than placebo group [difference: £1120 (95% confidence interval £56 to £2184)]. In the cost-effectiveness analyses, mean raw and adjusted outcome scores and costs of the complete cases samples showed no differences between groups. Limitations Our study has four important potential limitations: (1) we dropped the proposed carbamazepine group; (2) the trial was not powered to investigate a mortality difference between the groups; (3) recruitment beyond February 2020, was constrained by the COVID-19 pandemic; and (4) generalisability is limited by recruitment of participants from old-age psychiatry services and care homes. Conclusions The data suggest mirtazapine is not clinically or cost-effective (compared to placebo) for agitation in dementia. There is little reason to recommend mirtazapine for people with dementia with agitation. Future work Effective and cost-effective management strategies for agitation in dementia are needed where non-pharmacological approaches are unsuccessful. Study registration This trial is registered as ISRCTN17411897/NCT03031184. Funding This project was funded by the National Institute for Health and Care Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 27, No. 23. See the NIHR Journals Library website for further project information. Plain language summary It is common for people with Alzheimer’s disease to experience agitation, for example feeling restless or unsettled. If left untreated, agitation can lead to poorer quality of life and increased hospitalisation and strain for family carers. Often these symptoms are treated with medications that are usually used to manage psychosis (antipsychotic drugs), but such medication has limited effectiveness and can cause serious adverse effects to patients, including risk of increased death. Two medications that are already commonly prescribed for other health issues, mirtazapine (an antidepressant) and carbamazepine (a drug used to treat epilepsy), had been identified as a possible alternative way of treating agitation in Alzheimer’s disease that might not have the harms associated with antipsychotic medication. In this study, we compared the effects of giving mirtazapine or carbamazepine with a dummy drug (placebo) in people with Alzheimer’s disease who were experiencing agitation. The results of the study showed that neither medication was any more effective than the placebo in reducing agitation over 12 weeks in terms of improving symptoms, or in economic terms. Mirtazapine may lead to additional carer costs as compared to placebo. The study findings are stronger for mirtazapine than carbamazepine because the carbamazepine arm was stopped when it had recruited less than half the numbers needed. That was done because the study was not recruiting quickly enough to support both the mirtazapine and the carbamazepine arms. The findings from this study show that mirtazapine should not be recommended to treat agitation in Alzheimer’s disease. More work is needed to formulate effective ways and to test new drug and non-drug treatments for agitation in dementia. Scientific summary Background Agitation is common in people with dementia and impacts negatively on the quality of life of both people with dementia and carers. Non-drug patient-centred care is the first-line treatment, but there is a need for other treatment when this fails. Current evidence is sparse on safer and effective alternatives to antipsychotics. We assessed efficacy and safety of mirtazapine (an antidepressant) and carbamazepine (an anticonvulsant) prescribed for agitation in dementia. Aim To assess the safety, clinical and cost-effectiveness of mirtazapine and carbamazepine in the treatment of agitation in dementia. Primary objectives To determine if mirtazapine is more clinically effective in reducing agitated behaviours in dementia than placebo, measured by Cohen-Mansfield Agitation Inventory (CMAI) score 12 weeks post randomisation. To determine if carbamazepine is more clinically effective in reducing agitated behaviours in dementia than placebo measured by CMAI score 12 weeks post randomisation. Methods Design Pragmatic, phase III, multicentre, double-blind, superiority, randomised, placebo-controlled trial of the clinical effectiveness of mirtazapine and carbamazepine over 12 weeks. Intervention (1) Mirtazapine, (2) carbamazepine and (3) placebo. Target dose: 45 mg of mirtazapine or 300 mg of carbamazepine. Inclusion and exclusion criteria Patients were eligible if the following criteria were met: a clinical diagnosis of probable or possible Alzheimer’s disease a diagnosis of co-existing agitated behaviours evidence that the agitated behaviours have not responded to management an assessment of CMAI (Long Form) score of 45 or greater written informed consent to enter and be randomised into the trial availability of a suitable informant. Exclusion criteria included: current treatment with antidepressants [including Monoamine Oxidase Inhibitors (MAOIs)], anticonvulsants or antipsychotics contraindications to the administration of mirtazapine or carbamazepine patients with second-degree atrioventricular block patients with a history of bone marrow depression or history of hepatic porphyrias cases too critical for randomisation (i.e. where there is a suicide risk or where the patient presents a risk of harm to others) female subjects under the age of 55 years of childbearing potential. Setting Participants were drawn from existing patients and new patient referrals to old age psychiatric services, memory clinics, specific Participant Identification Centres, primary care centres and those in care homes in 26 UK sites. Consent Capacity to consent was assessed before proceeding with the consent process and included consideration of the provision of assent by the patient and consent on their behalf by their legal representative. If the patient had capacity to consent, the carer consented to the provision of information on data for measures on the patient (e.g. CMAI) and also on themselves in terms of impact. Randomisation and blinding Participants were allocated in a 1 : 1 : 1 ratio (up to the discontinuation of the carbamazepine arm and 1 : 1 thereafter) to receive placebo or carbamazepine or mirtazapine, together with treatment as usual. Random allocation was block stratified by centre and type of residence (care home vs. own household) with random block lengths of three or six up to the discontinuation of the carbamazepine arm and thereafter of two or four. The trial was double-blind, with drug and placebo identically encapsulated. Referring clinicians, participants, the trial management team and the research workers who did baseline and follow-up assessments were masked to group allocation. Outcomes Primary outcome CMAI score (Long Form) at 12 weeks. Secondary outcomes Costs derived from Client Service Receipt Inventory, and quality-adjusted life-years from cost data alongside supplemented information from Dementia-Specific Quality of Life and EuroQol-5 Dimensions, five-level version interviews 12 weeks post randomisation. CMAI score and cost at 6 weeks post randomisation. Patient and carer quality of life, and carer outcomes at 6 and 12 weeks post randomisation. Adverse events from week 0 to week 16 and adherence at 6 and 12 weeks post randomisation. CMAI score, adverse events and adherence at 6 and 12 weeks, conditional on evidence of effectiveness of Investigational Medicinal Product over placebo. Longer-term follow-up: CMAI score, institutionalisation, death and clinical management at 26 and 52 weeks post randomisation. Sample size and statistical analysis An initial calculated sample size of 400 (randomised 1 : 1 : 1) provided 90% power using two-sided 5% significance tests to detect a drug versus placebo mean difference in CMAI score at 12 weeks of 6 points. This equated to an effect size of d = 0.4 (assuming a common standard deviation of 15) or a clinically significant 30% decrease in CMAI from placebo to active drug. With a realistic 15% attrition, a sample of 471 (157 per arm) was aimed for. Mid-trial, with the discontinuation of the carbamazepine arm, the sample size calculation was revisited with emerging data and it was adjusted so that the aim (excluding those randomised to carbamazepine) was for an overall sample of 222 (randomised 1 : 1) to provide 80% power using two-sided 5% significance tests to detect a mirtazapine versus placebo mean difference in CMAI score at 12 weeks of six points, assuming attrition of no more than 10%. Analyses were based on intention-to-treat (all participants were analysed according to the group to which they were randomised, irrespective of the treatment or dose received). The primary outcome (CMAI at 12 weeks) was analysed using a general linear regression model including baseline CMAI score as a covariate. General linear regression models were created for secondary outcomes. Economic evaluation The primary outcome for the economic evaluation was the incremental cost per six-point difference in CMAI score at 12 weeks, from a health and social care system perspective. Patient and public involvement Ensuring the involvement of people living with dementia and their family carers was integral to the Study of Mirtazapine for Agitated Behaviours in Dementia (SYMBAD) trial from the application for funding and trial design stage through to its conduct, analysis and communication. SN was a co-applicant and led on public/carer involvement in the trial throughout, and she was supported by a Lived Experience Advisory Panel (LEAP) group hosted by Sussex Partnership Foundation Trust (SPFT) co-ordinated by JF and the NIHR DeNDRoN (Dementias and Neurodegenerative Diseases Research Network) group. Protocol change Due to slower than expected recruitment the carbamazepine arm was discontinued in August 2018 when 40 people had been randomised to it. This summary therefore focusses on the mirtazapine versus placebo comparisons. Results Between January 2017 and February 2020, 204 participants were recruited and randomised to either the mirtazapine (n = 102) or placebo arm (n = 102). Mean CMAI scores at 12 weeks were not significantly different between participants allocated to receive mirtazapine and placebo [adjusted mean difference −1.74, 95% confidence interval (CI) −7.17 to 3.69; p = 0.53, direction of change in favour of mirtazapine but not statistically significant]. The number of controls with adverse events [65/102 (64%)] was similar to that in the mirtazapine group [67/102 (66%)]. There were more deaths in the mirtazapine group (n = 7) by week 16 than in the control group (n = 1), with post hoc analysis suggesting this was of marginal statistical significance (p = 0.065), but this difference did not persist at 6- and 12-month follow-ups. The cost-effectiveness analyses similarly showed no evidence of benefit of mirtazapine over placebo, and no difference in costs between groups at 12 weeks. The carbamazepine arm closed in August 2018 when there had been 40 randomisations to that group, we therefore do not have statistical power for comparisons with placebo. However, exploratory analyses using the same modelling as for mirtazapine versus placebo showed there was also little evidence of any benefits compared to placebo (adjusted mean difference 2.46, 95% CI −5.01 to 9.93; p = 0.52), with similar levels of adverse events reported [27/40 (68%)]. Conclusions This is a trial with negative findings but important clinical implications. The data suggest that mirtazapine is not clinically effective or cost-effective (compared to placebo) for clinically significant agitation in dementia. Our findings suggest that there is little reason to recommend the use of mirtazapine for people with dementia who experience agitation. Effective and cost-effective management strategies for agitation in dementia are needed, particularly where non-pharmacological approaches have been unsuccessful, and for people with dementia and their carers living in community settings. Trial registration This trial is registered as ISRCTN17411897 and ClinicalTrials.gov as NCT03031184. Funding This project was funded by the National Institute for Health and Care Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment, Vol. 27, No. 23. See the NIHR Journals Library website for further project information.
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