Depression is a mental condition in which one feels exhausted, worthless, helpless, hopeless and desperate. lt affects 10-12% population of the Western countries. With out treatment, symptoms can last for weeks, rri.onths and years. Appropriate treatment can help most people who suffer from depression. The antidepressant class of drugs are well-known and widely used today. They are classified according to their principal mechanism of action: selective norepinefrine reuptake inhibitors (SNRI), selective serotonin reuptake inhibitors (SSRI), norepinefrine and serotonin reuptake inhibitors (NSRI), dopamin and norepinefrine reuptake inhibitors (DNRI), serotonin receptor modulators (SARI and NaSSA) and monoamine oxidase inhibitors (MAOI). New generations of antidepressants, such as SSRis, have more favourable side effect and pharmacokinetic profiles then the older generations of antidepressants, which has resulted in improved patient compliance and therapeutic outcomes for patients with major depressive disorder.