SNRIs

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Summary

Serotonin-norepinephrine reuptake inhibitors, abbreviated SNRIs, are a class of medications that increase serotonin and norepinephrine levels in the brain. SNRIs are useful in treating depression, anxiety, and chronic pain. Notably, SNRIs have the potential to cause serotonin syndrome, a life-threatening medical emergency. As a reminder, with serotonin syndrome the body is experiencing overactive everything - tachycardia, hypertension, hyperactive reflexes, diarrhea, and so on. This risk for serotonin syndrome is increased if SNRIs are combined with any other serotonin-altering substances, like St. John’s Wort or MAOIs. SNRIs can also cause sexual dysfunction.

Key Points

  • Key Drugs
    • Duloxetine
    • Venlafaxine
    • Levomilnacipran
    • Desvenlafaxine
    • Mechanism
      • Antidepressant
        • Increases serotonin and norepinephrine in the synapses by inhibiting their reuptake.
    • Clinical Use
      • Depressive Disorders
      • Anxiety Disorders
        • Generalized anxiety disorder (GAD)
        • Social anxiety disorder
        • Panic disorder
        • Post-traumatic Stress Disorder (PTSD)
      • Chronic pain
        • Diabetic neuropathy
        • Fibromyalgia
        • Chronic back pain/osteoarthritis
    • Side Effects and Adverse Reactions
      • Risk of Side Effects Increased with (avoid!)
        • St. John's Wort
        • MAOIs
        • Both the above can increase risk for serotonin syndrome
      • Serotonin Syndrome (think overactive everything)
        • Hyperthermia, Sweating
        • Tachycardia, hypertension
        • Muscle rigidity, loss of muscle coordination
        • Dilated pupils
        • Diarrhea
        • Agitation or restlessness
        • Confusion
        • Headache
        • Shivering
        • Goosebumps
        • Do not take concurrently with other serotonin altering medications
          • SSRIs
          • MAOIs
          • St John’s Wort
      • Increased risk of suicidal thoughts or behavior
        • Priority!
        • Seen at the beginning of therapy but should diminish over time
        • The patient will receive an increase in energy before they experience an increase in mood. Patients, especially young adults, need to be monitored for increased suicidal ideation, as they may now have the energy to follow through with the suicide plan
      • Sexual dysfunction
        • If patient is still experiencing sexual dysfunction after 2-4 weeks of treatment initiation, they should be encouraged to report this to the provider for a possible change in medication
      • Hepatotoxicity
        • Teach the patient to avoid alcohol
      • Withdrawal syndrome
        • Headache, nausea, visual disturbances, anxiety, dizziness, tremors
        • Withdraw from medication gradually