Classification of different antidepressant drugs

Psychiatrists started using the antidepressant drugs in treatment of mode changing cases in the beginning of the fifties of the last century. The first trials were the off-label usage of some anti – tuberculosis drugs that showed a noticeable effect in changing the patient’s mode. After that period, there are several categories that emerged and psychiatrists started using it as specific treatment for depressant patients.

The first antidepressant category is the Monoamine Oxidase Inhibitor (MAOI), this category was used for a very long time as the last drug of choice because of its irreversible action on the monoamine neuro transmitter but now with the new members of this category, the action is reversible and could be used as first choice of treatment of depression. It mainly acts on monoamine oxidase enzyme to prevent the degradation of monoamine but it can interact with the food intake of the patient in unfavorable way.

The second category is the tricyclic antidepressant (TCA). This category was more prevalent in the past and was considered a first line of treatment but recent researches proved that its effect was slightly elevated than the placebo treatment so; it is now replaced with the newer antidepressant drugs that we will discuss later on. While tricyclic antidepressants are not as addictive as MAOI but they could be more dangerous as the therapeutic dose and the lethal dose are not far from each other. TCA is metabolized in the liver through cytochrome 450 so, if the patient is taking another treatment that affect cytochrome 450 then TCA toxicity may occur easily.

The third category of antidepressant drugs is the tetracyclic antidepressant (TeCA). These antidepressant drugs are nearly the same as the previous category except in their molecular structure as they contain four rings while the former category contains only three rings. They are also used to treat other ailments like insomnia and anorexia beside treating depression.

The next category is the selective serotonin reuptake inhibitor drugs (SSRI). This category is more used these days because of its better effect and less addictiveness for the patient. Its mode of action is very simple as it prevents the presynaptic cell from reabsorbing the neuro – transmitter leaving an adequate amount available for the post synaptic cell to absorb. This action relieves depression through less period of time with a better safety margin.

The last category of these drugs is the serotonin-norepinephrine reuptake inhibitor (SNRI). This category acts upon two neuro- transmitters, serotonin and norepinephrine. The dual action of this category makes it more potent to treat depression than SSRI and it is widely used today to treat depression and considered the first line of treatment.