C OLIVIER
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Blog #12

12 May 2021, 13:42 Publicly Viewable

Classification of drugs

Selective Serotonin Re-uptake Inhibitors (SSRIs)
  • Fluoxetine
  • Citalopram
  • Escitalopram
  • Paroxetine
  • Sertraline
Serotonin Norepinephrine Re-uptake Inhibitors (SNRIs)
  • Duloxetine
  • Venlafaxine
  • Levomilnacipran
Selective Norepinephrine Re-uptake Inhibitors (NARIs)
  • Reboxetine
Tricyclic Antidepressants

Secondary amine:

  • Nortriptyline
  • Desimipramine
  • Lofepramine
 

Tertiary amine:

  • Amitriptyline
  • Imipramine
  • Trimipramine
  • Chlorimipramine
  • Dothiepine
  • Butriptyline
5-HT Receptors Modulators
  • Trazodone
  • Vortioxetine
Monoamine Oxidase Inhibitors (MAOIs)
  • Tranylcypromine
  • Moclobemide
  • Selegeline
Tetracyclic and Unicyclic
  • Mianserin
  • Mirtazepine
  • Bupropione
Circadian Rhythm Regulators
  • Agomelatine

What do the existing drugs all have in common regarding their mechanisms of action?

The antidepressants inhibit reuptake of neurotransmitters through selective receptors, thereby increasing the concentration of specific neurotransmitter around the nerves in the brain.

How long does it take for the antidepressive effects of these drugs to appear? What is the reason for this?

  • It takes approximately four to six weeks for antidepressant medications to reach their full therapeutic effect.
  • n people with depression, G proteins tended to congregate in lipid rafts, areas of the membrane rich in cholesterol. Stranded on the rafts, the G proteins lacked access to a molecule called cyclic AMP, which they need in order to function. 
  • AD's accumulates in the lipid rafts over time and as they do so, G proteins in the rafts decreases.
  • It's likely that this effect on the movement of G proteins out of the lipid rafts towards regions of the cell membrane where they are better able to function is the reason these antidepressants take so long to work.

Difference

  TADs SSRIs
EFFICACY
  • Mixed and variable blockade of NET and SERT.
  • Highly selective blockade of SERT
  • Little effect on NET
SIDE EFFECTS
  • Sympathomimetic: tremors
  • Anticholinergic: dry mouth
  • CVS: orthostatic hypotension
  • Psychosis
  • Convulsions
  • Metabolic: weight gain
  • Anticholinergic
  • EPS
  • Anxiety
  • Sexual dysfunction
  • Withdrawal syndrome
  • GIT disturbances 
SAFETY
  • Cause coma, cardio toxicity and convulsions
  • CYP inhibition

What is the action of mirtazapine?

  • NaSSA (NA & Specific Serotonin Antidepressant)
  • Blocks alpha 2, 5-HT2A, 5-HT3
  • Blockade of inhibitory alpha 2 receptors advance both NA (autoreceptor) & 5-HT (heteroreceptor) release.
  • Indirect stimulation of 5-HT1A
  • Blocks 5-HT3 as well as 5-HT2

What is the action of venlafaxine?

  • Moderately selective blockade of NET and SERT
  • More potent for 5-HT

What is the action of agomelatine?

  • Melatonin 1 and -2 agonist and 5-HT2C antagonist
  • 5-HT2C antagonism: disinhibition of DA and NA release in FC (increase DA and NA release)