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.
Keywords: AGITATION; ALZHEIMER’S DISEASE; CARBAMAZEPINE; DEMENTIA; MIRTAZAPINE; RCT.
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.