RESUMEN
Background: The experimental therapeutics approach that combines a placebo-controlled clinical trial with translational neuroscience methods can provide a better understanding of both the clinical and physiological effects of pharmacotherapy. We aimed to test the efficacy and tolerability of low-dose augmentation with buprenorphine (BPN) for treatment-resistant depression, combined with multimodal assessment of target engagement. Methods: In this multisite randomized clinical trial, 85 participants ≥50 years of age with a major depressive episode that had not responded to venlafaxine extended release were randomized to augmentation with BPN or placebo for 8 weeks. The primary outcome measure was the Montgomery-Åsberg Depression Rating Scale. In addition, three linked experiments were conducted to test target engagement: 1) functional magnetic resonance imaging using the monetary incentive delay task, 2) brain positron emission tomography of healthy participants using a novel kappa opioid receptor antagonist tracer [11C]LY2795050, and 3) transcranial magnetic stimulation measure of cortical transmission after daily BPN administration. Results: The mean ± SD dosage of BPN was 0.59 ± 0.33 mg/day. There were no significant differences between the BPN and placebo groups in Montgomery-Åsberg Depression Rating Scale changes over time or adverse effects. BPN administration had minimal effects on functional magnetic resonance imaging blood oxygen level-dependent responses in regions involved in reward anticipation and response, no significant displacement of kappa opioid receptor radioligand in positron emission tomography imaging, and no significant changes in transcranial magnetic stimulation measures of inhibitory and excitatory cortical transmission. Conclusions: Our findings suggest a lack of clinical effect of low-dose BPN augmentation and lack of target engagement with this dosage and physiological probes.
RESUMEN
Importance: Treatment-resistant depression (TRD) is common in older adults. Bilateral repetitive transcranial magnetic stimulation (rTMS) of the dorsolateral prefrontal cortex for 48 minutes has demonstrated efficacy in TRD. Theta burst stimulation (TBS), a newer form of rTMS, can also be delivered bilaterally using left intermittent TBS and right continuous TBS for only 4 minutes. Objective: To establish the effectiveness and tolerability of TBS compared with standard rTMS in older adults with TRD. Design, Setting, and Participants: In this randomized noninferiority trial with open treatment and blinded assessors, recruitment occurred between December 2016 and March 2020. The trial was conducted at the Centre for Addiction and Mental Health in Toronto, Ontario, Canada and included outpatients 60 years and older with a diagnosis of depression, moderate severity, and nonresponse to 1 or more antidepressant trial of adequate dosage and duration or intolerance of 2 or more trials. Interventions: Participants were randomized to receive a course of 4 to 6 weeks of either bilateral standard rTMS or TBS. Main Outcomes and Measures: The primary outcome measure was change in Montgomery-Åsberg Depression Rating Scale; secondary outcome measures included the 17-item Hamilton Rating Scale for Depression, Quick Inventory of Depressive Symptomatology (16-item) (self-report), and dropout rates. A noninferiority margin of 2.75 points was used for the primary outcome. All participants who attained the primary completion point of 4 weeks were analyzed. Results: A total of 87 participants (mean [SD] age, 67.1 [6.7] years; 47 [54.0%] female) were randomized to standard bilateral rTMS and 85 (mean [SD] age, 66.3 [5.3] years; 45 [52.9%] female) to TBS, of whom 85 (98%) and 79 (93%) were assessed for the primary outcome, respectively, whereas tolerability was assessed in all randomized participants. In the rTMS group, 4 (4.6%) were American Indian, reported other, or preferred not to answer; 5 (5.8%) were Asian; and 78 (89.7%) were White. In the TBS group, 6 (7.1%) were Asian, 2 (2.4%) were Black or reported other, and 77 (90.3%) were White. Mean (SD) Montgomery-Åsberg Depression Rating Scale total scores improved from 25.6 (4.0) to 17.3 (8.9) for rTMS and 25.7 (4.7) to 15.8 (9.1) for TBS (adjusted difference, 1.55; lower 95% CI -0.67), establishing noninferiority for TBS. The all-cause dropout rates were relatively similar between groups (rTMS: 2 of 87 [2.3%]; TBS: 6 of 85 [7.1%]; P = .14; χ2 = 2.2). Conclusions and Relevance: In older adults with TRD, bilateral TBS compared with standard bilateral rTMS achieved noninferior reduction in depression symptoms. Both treatments had low and similar dropout rates. Using TBS rather than rTMS could increase access to treatment several-fold for older adults with TRD. Trial Registration: ClinicalTrials.gov Identifier: NCT02998580.
