When do you consider low-dose buprenorphine for the management of treatment resistant depression?

At doses of 0.25-2 mg, buprenorphine has potent kappa opioid receptor antagonism, and this conveys anxiolytic and antidepressant activities. It can be used in an augmentation mode with other antidepressants. See (Karp et al., PMID 25191915; Fava et al., PMID 26869247; Thase et al., PMID 31254971; Fa...

Because of the potential for nausea/vomiting, it is important to give a test dose of 0.25 mg daily orally. If that is tolerated over a week, increase to 0.5 mg daily for a week, then 1 mg daily, depending on response.