- According to the biological theory of depression, reduction of 3 monoamines in our brain (serotonin, norepinephrine and dopamine); also known as trimonoaminergic depletion is responsible for depression
- Antidepressants works primarily by decreasing the sensitivity of the neuroreceptors of the any of the 3 monoamines specified, in a long term basis.
Family of the antidepressants:
- Tricyclic antidepressants (TCA): Inhibits reuptake of all 3 monoamines
- Selective serotonin reuptake inhibitor (SSRI)
- Serotonin and norepinephrine reuptake inhibitors (SNRI)
- Norepinephrine-dopamine reuptake inhibitor (NDRI).
Uses of TCA:
- Clomipramine: Gold standard drug for OCD
- Imipramine: Nocturnal enuresis (DOC: Desmopressin)
- Amitriptyline: Tension type headache
- Nortriptyline: Post-stroke depression.
- Fluvoxamine has the shortest half life among all SSRIs; so, it has the highest risk of drug discontinuation syndrome
- Fluoxetine has the longest half life among all SSRIs; so, it has no risk of drug discontinuation syndrome
- SSRIs are the DOC in following conditions:
- Atypical depression
- Premenstrual dysphoric disorder
- Panic disorder (Chronic anxiety)
- Post-traumatic stress disorder (PTSD)
- Premature ejaculation.
- MC side effect of SSRI is nausea and vomiting (due to increased amount of serotonin acting on CTZ area of brain)
- Most characteristic side effect of SSRI is delayed ejaculation; for this property, SSRIs are used in the treatment of premature ejaculation.
Miscellaneous uses of SNRI (other than depression):
- Venlafaxine: MC-ly used SNRI
- Duloxetine: Fibromyalgia, diabetic neuropathy & chronic pain syndrome
- Atomoxetine: ADHD
- Sibutramine: Marketted for treatment of obesity, withdrawn due to cardiovascular adverse events.
- Bupropion is prescribed as an aid for smoking cessation. It reduces the severity of nicotine cravings and withdrawal symptoms.
- NaSSA: Mirtazapine
- SARI: Trazodone
- SSRE: Tianeptine
- SPARI: Vilazodone.
*NaSSA: Noradrenergic specific serotonergic agent, SARI: Serotonergic antagonist & reuptake inhibitor, SSRE: Selective serotonin reuptake enhancer, SPARI: Serotonin partial agonist & reuptake inhibitor.