There are no official guidelines to assist in answering this question. I will search for relevant research papers instead.
The FDA Drug Labels for escitalopram (PO), duloxetine (PO) do not address this question.
From the Research
Combination Therapy of Escitalopram and Duloxetine
There are no research papers to assist in answering this question regarding the specific instance in which taking both escitalopram (Selective Serotonin Reuptake Inhibitor - SSRI) and duloxetine (Serotonin-Norepinephrine Reuptake Inhibitor - SNRI) together would be warranted.
Efficacy and Safety of Escitalopram and Duloxetine
- The studies 1, 2, 3, 4, 5 compared the efficacy and safety of escitalopram and duloxetine in the treatment of major depressive disorder.
- Escitalopram was found to be at least as effective as duloxetine in the treatment of major depressive disorder, with a better tolerability profile 2, 3.
- Duloxetine was found to be non-inferior to escitalopram in terms of onset of antidepressant action 4.
- Both drugs demonstrated similar remission rates over the course of an 8-month study, with similar improvement on most efficacy measures 5.
Safety and Tolerability
- Escitalopram was found to have a lower incidence of treatment-emergent adverse events compared to duloxetine 2.
- Duloxetine was associated with a higher incidence of nausea, dry mouth, vomiting, yawning, and irritability compared to escitalopram 4.
- Escitalopram was found to have a lower rate of discontinuation due to adverse events compared to duloxetine 2, 5.