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NEWER ANTIDEPRESSANT AGENTS
After the introduction of the Serotonin Reuptake Inhibitors (SRIs), newer agents with a wider spectrum of action were developed in an attempt to match the efficacy of the Tricyclic Antidepressants and Monoamine Oxidase Inhibitors but with a better side effect and safety profile. As these drugs are relatively new it is not yet clear that these goals have been achieved.
Venlafaxine and nefazodone are serotonin noradrenergic reuptake inhibitors (SNaRIs), Mirtazapine is a noradrenergic and specific serotonergic antidepressant (NaSSA) and Reboxetine is a noradrenaline reuptake inhibitor (NaRI).
At low doses, where serotonin reuptake inhibition predominates venlafaxine is very similar in action to the SRIs; at higher doses, noradrenaline reuptake inhibition also occurs.
Nefazodone inhibits the 5-HT2 receptor and this is thought to increase the binding of serotonin to the 5-HT1A receptor. Additionally, nefazodone causes weak inhibition of noradrenaline and serotonin reuptake.
Mirtazapine inhibits α2-adreoreceptors, 5-HT2 and 5-HT3 receptors. These results in increased noradrenaline and serotonin release; the later having its main affect on 5-HT1A-mediated neurotransmission.
Reboxetine it is a selective inhibitor of noradrenaline reuptake and has no serotonin effects.
This group includes: