This week on Medication Monday, we’re diving into SNRIs (Serotonin-Norepinephrine Reuptake Inhibitors) — a class of antidepressants with unique properties and a broad range of uses.
Mechanism of Action:
SNRIs block the reuptake of both serotonin (5-HT) and norepinephrine (NE), increasing their availability in the brain. The norepinephrine component can offer an “activating” effect for some individuals who may need an energy boost, especially those struggling with fatigue or pain.
- Major depressive disorder (MDD)
- Generalized anxiety disorder (GAD)
- Social anxiety disorder (SAD)
- Panic disorder (venlafaxine XR)
- Fibromyalgia (duloxetine)
- Chronic musculoskeletal pain (duloxetine)
- Diabetic peripheral neuropathic pain (duloxetine)
- Menopausal hot flashes (venlafaxine)
- PTSD
- Neuropathic pain syndromes
We may consider SNRIs when patients experience both mood and physical symptoms (e.g., pain, fatigue) or when an SSRI alone hasn’t provided sufficient improvement.
- Helpful for patients with comorbid pain and depression/anxiety
- Some patients benefit from the activating norepinephrine component, especially if fatigue is prominent
- Evidence for effectiveness in perimenopause for mood and vasomotor symptoms
- Can increase blood pressure (especially venlafaxine at higher doses)
- Risk of withdrawal symptoms when discontinuing
- Possible sexual side effects, GI upset, insomnia
- Venlafaxine (Effexor XR): More serotonin reuptake at lower doses, more norepinephrine reuptake at higher doses.
- Desvenlafaxine (Pristiq): Active metabolite of venlafaxine, more predictable pharmacokinetics.
- Duloxetine (Cymbalta): Broad indications including pain conditions.
- Levomilnacipran (Fetzima): More potent norepinephrine reuptake inhibition than serotonin — may feel more “activating.”
- Venlafaxine XR is sometimes used off-label for hot flashes in perimenopause.
- Duloxetine is commonly chosen when chronic pain is a prominent symptom.
- Levomilnacipran tends to be more energizing and may not be ideal if anxiety is prominent.
- Why tapering can be difficult:
- SNRIs, especially venlafaxine, have a short half-life, so withdrawal symptoms (“discontinuation syndrome”) can occur if stopped abruptly.
- Symptoms may include dizziness, nausea, headache, fatigue, irritability, “brain zaps.”
- At Ruby Mental Wellness, we carefully follow the newly-published deprescribing guidelines:
- Gradual, individualized taper plans
- Patient education on what to expect
- Close monitoring for emergent withdrawal symptoms
- Supportive strategies to minimize discomfort
✅ Key takeaway:
SNRIs are versatile medications that can address mood, anxiety, pain, and perimenopausal symptoms. Their dual action on serotonin and norepinephrine makes them unique, but careful selection, monitoring, and tapering are key to successful use.