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Depression:
Depression occurs due to decreased activity of Noradrenaline (NA) and
5-HydroxyTryptamine (5-HT).
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Antidepressants drugs
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Typical antidepressants
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Atypical
antidepressants
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Tricyclic
antidepressants:
a. Nor adrenaline and 5-HT reuptake inhibitors:
·
Imipramine
·
Amitriptyline
·
Clomipramine
·
Dothiepin
·
Trimipramine
·
Doxepin
b. Predominantly Nor adrenaline reuptake inhibitors:
·
Desipramine
·
Amoxapine
·
Nortriptyline
·
Reboxetine
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Selective
serotonin reuptake inhibitors:
·
Fluoxetine
·
Paroxetine
·
Sertraline
·
Fluvoxamine
·
Citalopram
·
Escitalopram
·
Dapoxetine
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MAO
inhibitors:
a. Non selective MAO
inhibitors:
·
Phenelzine
·
Isocarboxazid
·
tranylcypromine
b. Selective MAO-B
inhibitors:
·
Selegeline
c. Reversible MAO-A
inhibitors:
·
Clorgyline
·
Moclobemide
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·
Trazodone
·
·
Duloxetine
·
Mianserin
·
Tianeptin
·
Amineptin
·
Milnacipran
·
Mirtazapine
·
Nafazodone
·
Atomoxetine
·
Bupropion
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Mechanism of action:
Typical
antidepressants: They increase NA and 5-HT level
by inhibiting metabolism or reuptake of NA or 5-HT.
Atypical
antidepressants: They may or may not increase NA
or 5-HT level or have different mechanism of action.
1st
generation antidepressant: Inhibit reuptake of NA
and 5-HT by inhibiting NET and SERT. But
also have anticholinergic, antiadrenergic and antihistaminergic effect. e.g. TCA,
MAOI
2nd
generation antidepressant: Inhibit reuptake of NA
or 5-HT by inhibiting NET or SERT. But
have no anticholinergic, antiadrenergic and antihistaminergic effect. E.g.
SSRI AND SNRI.
TCA:They inhibit reuptake of NA and 5-HT by inhibiting NET and
SERT. But also have anticholinergic,
antiadrenergic and antihistaminergic effect.
SSRI: They inhibit reuptake of 5-HT by inhibiting SERT but not NET (NA).
No anticholinergic and antiadrenergic effect
SNRI: They inhibit reuptake of 5-HT and NA by inhibiting SERT and NET
but no anticholinergic, antiadrenergic and antihistaminergic effect.
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Tricyclic
antidepressants v/s SSRI
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Tricyclic
antidepressants:
Cause sedation
Cause weight gain
Anticholinergic action like blurred
vision, constipation
Induce seizures
Hypotension
They inhibit reuptake of NA as well as
5-HT
1st generation antidepressant
Low safety margin
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SSRI:
No sedation
No weight gain
No anticholinergic action
No seizure induction
No Hypotension
They inhibit reuptake of 5-HT only
2nd generation antidepressant
Good safety margin
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TCA:
Ø Low safety margin
Ø Amoxapine (inhibit D2 receptor also) is metabolite of Loxapine
Ø Also used for nocturnal enuresis.
Ø TCA AND MAOI also known as 1st generation
antidepressant.
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SSRI:
Ø Good safety margin
Ø Cause anxiety
Ø Inhibit ejaculation
Ø Fluvoxamine: shortest acting SSRI
Ø Fluoxetine: longest acting SSRI as well as longest acting
antidepressant (for juvenile depression-only effective antidepressant)
Ø SSRI are 1st choice of drug in depression, OCD,
Phobias.
Ø Paroxetine highly teratogenic SSRI.
Ø SSRI and SNRI also known as 2nd generation
antidepressant.
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MAO
INHIBITORS:
Ø Non selective MAO inhibitors show cheese reactions.
Ø Serotonin syndrome develop if SSRI are given with or after MAO
inhibitors
Ø They increase risk of seizures
Ø Reversible MAO inhibitors not show cheese reactions.
Ø Moclobemide is good choice for elder patient.
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ATYPICAL
ANTIDEPRESSANTS:
Ø Venlafaxine and Duloxetine inhibit reuptake of NA and 5-HT but not
have anticholinergic activity. They are also known as SNRI
Ø Amineptin and Tianeptin
increase serotonin reuptake.(Challenge 5-HT hypothesis of depression)
Ø For smoking cessation Bupropion also used.
Ø Bupropion inhibit uptake of dopamine and NA.
Ø Mianserin: It blocks alpha 2 receptor, 5-HT2 and H1
receptor but not inhibiting uptake of NA or 5-HT.
Ø Trazodone:inhibit alpha receptor
but weakly inhibit 5-HT2. Weakly inhibit uptake of 5-HT.
Ø Mirtazapine: inhibit alpha-2 receptor and increase release of NA
and 5-HT.
Ø Nefazodone shortest acting antideprerssant
Ø Duloxetine used for chronic neuropathic pain.
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uses of
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