An Implementation Science Assessment of Intranasal Esketamine's Limited Integration into Mainstream Psychiatric Treatment.

Major Depressive Disorder is one of the most common mental illnesses worldwide, with oral antidepressant medication being the first-line psychopharmacological treatment option. The term Treatment Resistant Depression (TRD) is used to describe patients who remain symptomatic despite multiple trials of antidepressant medication. There had been limited FDA-approved treatment options for patients with TRD, but in 2019, intranasal esketamine was approved by the FDA for patients with TRD after safety and efficacy were established in the drug development clinical trial program. Since approval, multiple researchers have explored esketamine's effectiveness in real-world treatment settings. Despite established efficacy and effectiveness, most psychiatric treatment settings do not offer intranasal esketamine. This limited implementation is reviewed using the Consolidated Framework for Implementation Research (CFIR), and steps forward are proposed to improve accessibility for patients with TRD.