Effexor XR Effexor XRis aserotonin-norepinephrine reuptake inhibitor (SNRI)antidepressant FDA-approved to treatdepressionas well asanxietydisorders. However, some take it off-label (for a non-FDA-approved use) to treat cataplexy from narcolepsy.2 Common side effects include: Nausea Dry mouth Appetite...