Clinical and cost-effectiveness of lithium versus quetiapine augmentation for treatment-resistant depression: a pragmatic, open-label, parallel-group, randomised controlled superiority trial in the UK

Lithium and quetiapine are first-line augmentation options for treatment-resistant depression; however, few studies have compared them directly, and none for longer than 8 weeks. We aimed to assess whether quetiapine augmentation therapy is more clinically effective and cost-effective than lithium for patients with treatment-resistant depression over 12 months. We did this pragmatic, open-label, parallel-group, randomised controlled superiority trial at six National Health Service trusts in England. Eligible participants were adults (aged ≥18 years) with a current episode of major depressive disorder meeting DSM-5 criteria, with a score of 14 or higher on the 17-item Hamilton Depression Rating Scale at screening who had responded inadequately to two or more therapeutic antidepressant trials. Exclusion criteria included having a diagnosis of bipolar disorder or current psychosis. Participants were randomly assigned (1:1) to the decision to prescribe lithium or quetiapine, stratified by site, depression severity, and treatment resistance, using block randomisation with randomly varying block sizes. After randomisation, pre-prescribing safety checks were undertaken as per standard care before proceeding to trial medication initiation. The coprimary outcomes were depressive symptom severity over 12 months, measured weekly using the Quick Inventory of Depressive Symptomatology, and time to all-cause treatment discontinuation. Economic analyses compared the cost-effectiveness of the two treatments from both an NHS and personal social services perspective, and a societal perspective. Primary analyses were done in the intention-to-treat population, which included all randomly assigned participants. People with lived experience were involved in the trial. The trial is completed and registered with the International Standard Randomised Controlled Trial registry, ISRCTN16387615. Between Dec 5, 2016, and July 26, 2021, 212 participants (97 [46%] male gender and 115 [54%] female gender) were randomly assigned to the decision to prescribe quetiapine (n=107) or lithium (n=105). The mean age of participants was 42·4 years (SD 14·0 years) and 188 (89%) of 212 participants were White, seven (3%) were of mixed ethnicity, nine (4%) participants were Asian, four (2%) were Black, three (1%) were of Other ethnicity, and ethnicity was not recorded for one (1%) participant. Participants in the quetiapine group had a significantly lower overall burden of depressive symptom severity than participants in the lithium group (area under the between-group differences curve -68·36 [95% CI -129·95 to -6·76; p=0·0296). Time to discontinuation did not significantly differ between the two groups. Quetiapine was more cost-effective than lithium. 32 serious adverse events were recorded in 18 participants, one of which was deemed possibly related to the trial medication in a female participant in the lithium group. The most common serious adverse event was overdose, occurring in three (3%) of 107 participants in the quetiapine group (seven events) and three (3%) of 105 participants in the lithium group (five events). Results of the trial suggest that quetiapine is more clinically effective than lithium as a first-line augmentation option for reducing symptoms of depression in the long-term management of treatment-resistant depression, and is probably more cost-effective than lithium. National Institute for Health and Care Research Health Technology Assessment programme.