Medicine & USMLE


Psych Pharm
  1. Lithium
  2. Typical Antipsychotics
  3. Atypical Antipsychotics
  4. SSRIs
  5. SNRIs
  6. Tricyclic Antidepressants (TCAs)
  7. Monoamine Oxidase Inhibitors (MAOIs)
  8. Bupropion
  9. Mirtazapine
  10. Trazadone
  11. Vilazodone
  12. Vortioxetine
  13. Buspirone
  14. Varenicline


Trazodone is an antagonist or blocker of serotonin, H1, and alpha-1 adrenergic receptors. Trazodone can be used to treat major depressive disorder by modulating serotonin signaling in the brain. It can also be used off-label to treat insomnia due to its strong sedative effects. A major adverse effect of trazodone use is priapism, which is a painful erection lasting more than four hours independent of sexual arousal. Trazodone can also cause hypotension, serotonin syndrome, and nausea.

Key Points

  • Trazodone
    • Mechanism:
      • Blocks 5-HT2 receptors
        • Modulates but generally antagonizes 5-HT2 serotonin receptors
        • Also weakly inhibits serotonin reuptake
      • Blocks H1 receptors
        • Accounts for sedative use in treating insomnia
      • Blocks α1-adrenergic receptors
    • Indications
      • Treats Major Depressive Disorder
        • Used to treat depression in patients with insomnia
        • Usually high doses of trazodone are required to treat major depressive disorder.
    • Adverse effects
      • Causes Sedation (can help treat insomnia)
        • Often used off-label to treat insomnia for its strong sedative effects
      • Causes Priapism
        • Priapism refers to an erection lasting more than four hours independent of sexual arousal. Priapism is a dangerous condition because if left untreated it can lead to penile ischemia.  
      • Causes Postural Hypotension
        • Due to blockade of  α1-adrenergic receptors
      • Causes Serotonin Syndrome
        • Especially when used with other serotonin-modulating drugs (SSRIs, SNRIs, MAOIs, TCA’s, etc.)
      • Causes Nausea