In some western hemisphere countries, including the United States, Paxil (and Paxil CR) is the trade name for paroxetine. Paxil is considered to be one of the newer antidepressant medications. These newer medications have fewer side effects than older antidepressant drugs, and the side effects that do occur, are better handled by the individuals taking such medications. Paxil has been approved by the Food and Drug Administration (FDA) to treat obsessive-compulsive disorder (OCD) as well as panic disorders. Physicians have also legally prescribed Paxil for other ailments such as bulimia, premenstrual syndrome, alcohol and nicotine addiction.

Known as selective serotonin-specific reuptake inhibitors (SSRIs), these drugs are currently the most frequently prescribed antidepressant medications. Often referred to as a chemical imbalance by lay people, medical studies note that depression can be caused by an imbalance of the serotonin system in the brain.

Nerve cells in the brain communicate with each other by passing messages through small gaps between the cells - synapse. The cells sending information release neurotransmitters. One such neurotransmitter is known as serotonin. If the released serotonin is accepted by the recipient cell, there is communication between the cells and messages are forwarded. However, some serotonin is lost in the process while other returns to the sending cell. SSRIs inhibit the reuptake of serotonin that is initially released, thereby increasing the level of serotonin available to facilitate cell to cell communication.

Based on the premise that depression is associated with a lack of stimulation of the recipient neuron at a synapse, to stimulate the recipient cell, SSRIs inhibit the reuptake of serotonin. By prescribing an SSRI medication such as Paxil, the reuptake of the serotonin is inhibited, thus allowing the neurotransmitter to remain in the synaptic gap longer than it normally would. This allows the receptor cell the opportunity to recognize serotonin over and over again with the expectation that recognition will occur and the recipient cell will then be fully stimulated.

SSRIs affect only the reuptake pumps responsible for serotonin, versus older antidepressants, which affect other neurotransmitters as well. Because of this, SSRIs are described as 'selective' and lack some of the side effects of the earlier drugs.

Before SSRIs were developed, more commonly prescribed antidepressant medications were known as tricyclic antidepressant, sometimes referred to as TCA. The effectiveness between the TCA medications versus SSRIs seems to be insignificant. However SSRIs have a high toxic dose which makes them less dangerous if a patient were contemplating suicide. Some general side effects caused by SSRIs are: nausea, headache, anxiety, restlenssness or trouble sleeping. Studies suggest that SSRIs such as Paxil may promote the growth of new neural pathways. Also, SSRIs may protect against neurotoxicity caused by other compounds as well as from depression itself.

Paxil prescription in North America has only been approved for patients 18 years of age or older.

On Dec 13, 2006, a U.S. Food and Drug Administration advisory panel recommended that black-box warnings on SSRIs be raised from 18 to 25 years old. Although the FDA is not obliged to follow the recommendations of its advisory committees, it generally does.