Definition and Classification of Antidepressant Drugs - Essay Example

Based on the mechanism of action, Anti-depressant drugs are divided into seven main categories. A brief description of their distinction in the mode of action is also described along with their examples.

TCAs: Tricyclic antidepressants block the reuptake of nor-epinephrine and increase its level. Examples include amitriptyline, imipramine, clomipramine, etc.

MAOIs: Monoamine-oxidase inhibitors inhibit the enzymes monoamine oxidase that degrades norepinephrine, serotonin, etc, thus increasing their levels. Examples include Tranylcypromine, Phenelzine, etc.

SSRIs: Selective Serotonin reuptake inhibitors block the reuptake of serotonin only. These include fluoxetine, fluvoxamine, etc.

SNRIs: Serotonin-norepinephrine reuptake inhibitors block uptake of both serotonin and norepinephrine. An example includes Venlafaxine.

NARI: Noradrenalin reuptake inhibitors block the reuptake of noradrenaline. An example includes Reboxetine.

RIMA: Reversible Inhibitors of Monoamine Oxidase-A inhibits the breakdown of three neurotransmitters i.e. dopamine, norepinephrine, and serotonin. An example is Moclobemide.

NaSSa: Noradrenergic and Specific Serotonergic Antidepressants increase the concentration of noradrenaline and serotonin in the synaptic cleft by inhibiting autoreceptors. An example includes Mirtazapine (Rxpgonline.com, 2014).

Selective serotonin reuptake inhibitor works by blocking serotonin reuptake. Reuptake is a natural phenomenon in which different neurotransmitters are naturally reabsorbed back by nerve cells of the brain. When a reuptake inhibitor like SSRI is used, it prevents the reabsorption of neurotransmitters as a result the level of neurotransmitters in the synaptic cleft increases, thus improving the communication between nerve cells and reinforcing those brain regions that are involved in mood regulation (Webmd.com, 2014).

It is also proposed that the main restorative outcome of SSRIs is observed in delayed neurochemical adaptation. According to this proposal, serotonin desensitizes certain receptors in the midbrain. These receptors are somatodendritic serotonin 1A autoreceptors. When these become desensitized the level of serotonin in crucial areas of the brain increases that may help combat different signs and symptoms of depression (Stahl, 1998).

These are different than TCAs as they only block the reuptake of serotonin and not of nor-epinephrine and cause fewer side effects than TCAs. Still, SSRIs show some side effects that include nausea, vomiting, dry mouth, headache, sweating, gastrointestinal discomfort, etc, and are given with caution in patients having suicidal tendencies. Examples of SSRI include fluoxetine, fluvoxamine, citalopram, sertraline, paroxetine, etc (Thebrain.mcgill.ca, 2014).