MAOIs act by inhibiting monoamine oxidase, a complex enzyme system that metabolizes excess serotonin and epinephrine. It holds the negativity of inducing potential life-threatening problems and therefore cannot be used in patients with congestive cardiac failure or in those with a history of liver disease. It can be dangerous for those who are hypersensitive to its ingredients. It should be used only when other available Antidepressant medications fail as treatment options for depression.
TCAs act mainly by inhibiting the reuptake of both norepinephrine and serotonin. Though the type of side effects experienced by the patient due to TCAs or MAOIs are many times similar, the frequency of these side effects is much less in the case of TCAs. Thus, TCAs enjoy a better rate of acceptance by the patients.
The SSRIs act by inhibiting the serotonin reuptake and are considered the most popular, effective and safe prescription medications. Prozac, a drug of this class, has shown significant success in the treatment of depression and prevention of suicide. It exhibits less potential side effects as compared to TCAs and MAOIs, and is well tolerated.
It should be noted that these three therapeutic groups share the similarity of relieving depressive symptoms in the same period of time (1 to 4 weeks). The SSRIs, because of their benefit of safety and tolerability, enjoy the stand of first-line agents. The TCAs are much cheaper than SSRIs and are preferred by patients who are unresponsive to other Antidepressants.
The SNRIs better serve a patient of depression by aiming to keep both serotonin and norepinephrine at the right level. The drug bupropion (novel Antidepressant) is unique in its efficiency to inhibit the reuptake of dopamine, serotonin and norepinephrine.