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Atypical Antidepressants, Enhance serotonergic effect: Antagonist effects…
Atypical Antidepressants
Bupropion
PK: Half-life of about 12 to 20 hours. Extensively liver metabolised by CYP2D6. Metabolites. eg. OH-bupropion have lower potency.
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Indication: major depression, smoking cessation (SR formulation for nicotine dependance)
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Adverse effects
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Agitation, headache, insomnia, seizure (high dose), aggravation of psychosis
Mirtazapine
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PK: 50% oral bioavailability. Extensively liver metabolised by CYP3A, CYP2D6 & CYP1A2). Half-life of about 20 to 40 hours.
Similar efficacy as TCAs, but higher affinity for H1 receptors
MOA: Noradrenergic/specific serotonergic antidepressant (NaSSA). Blocks alpha-2, 5-HT2A, 5-HT2C and 5-HT3 receptors
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Venlafaxine
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PK: liver metabolised by CYP2D6 & CYP3A4. Active metabolites: O-desmethylven. Short half-life of about 5 hours.
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Non-selective inhibitor of cholnergic, histaminergic and adrenergic receptors (like TCAs), but w/ improved AE profile
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Trazodone
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MOA: serotonin antagonist and reuptake inhibitors (SARI）Blocks 5-HT2A and 5-HT2C receptors. Also blocks H1 receptors.
PK: liver metabolised by CYP3A4. Active metabolite: m-chlorophenylpiperazine. Half-life of 6 to 12 hours
Indication: depression, neuropathic pain, panic disorder, cocaine withdrawal
Adverse effects
Hypotension, cardiac dysarrhythmia, agitation
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Duloxetine
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Indication: major depression, urinary incontinence, neuropathic pain, anxiety disorders
Adverse effects
Sedation, dizziness, sexual dysfunction
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Enhance serotonergic effect: Antagonist effects on the central presynaptic alpha-2-adrenergic receptors cause an increased release of serotonin and norepinephrine. Antagonism of 5-HTA, 5HT2C, and 5-HT3 receptors leads to the remaining serotonin concentration left to interact with the free 5-HT1 receptor. This interaction with the 5-HT1 receptor (particularly the 5-HT1A receptor) is what leads to antidepressant effects.