Antidepressant Poisoning

Basics

Description

  • Antidepressants are the most commonly prescribed psychiatric medications in the US
  • Patients who overdose on antidepressants may be on various antidepressants, divided into categories of SSRIs, SNRIs, and atypical (such as bupropion)
  • Antidepressants may be prescribed for multiple other indications, including chronic pain syndromes, anxiety, eating disorders, substance abuse, and sleep disorders
  • Tricyclic antidepressants (TCAs) are covered in a separate chapter

Etiology

Mechanism

  • SSRIs:
    • Increase serotonin at the synapse by preventing the reuptake of serotonin by the presynaptic neuron
    • SSRIs include paroxetine, fluoxetine, sertraline, citalopram, and escitalopram
  • SNRIs:
    • Similar to SSRIs, but also inhibit reuptake of norepinephrine
    • SNRIs include venlafaxine, desvenlafaxine, and duloxetine
  • Atypical antidepressants:
    • Have variable effects on serotonin, norepinephrine, and dopamine
    • Include bupropion, mirtazapine, and trazodone
    • Bupropion is the only pharmaceutical cathinone. It inhibits norepinephrine and dopamine reuptake and also has antagonism at nicotinic receptors
  • Atypical antipsychotics:
    • Most antipsychotics have activity at dopamine receptors, although variable agonism/antagonism depending on medication and dopamine receptor
    • Many have additional activity at serotonin, α-adrenergic, histamine, and muscarinic receptors
  • Antidepressants and antipsychotics have variable potassium and sodium channel blockade, and can lead to cardiotoxicity (QT and QRS prolongation, respectively)
  • Citalopram and escitalopram are significantly more likely to cause QTc prolongation than other SSRIs
  • Other than TCAs, bupropion is the antidepressant most associated with QRS widening in overdose

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