Paroxetine is a potent and selective serotonin reuptake inhibitor (SSRI) with currently approved indications for the treatment of depression, obsessive-compulsive disorder, panic disorder and social phobia. It is also used in the treatment of generalized anxiety disorder, post traumatic stress disorder, premenstrual dysphoric disorder and chronic headache. Paroxetine, a phenyl piperidine derivative, is the most potent inhibitor of the reuptake of serotonin (5-hydroxytryptamine, 5-HT) of all the currently available antidepressants including the class of SSRIs. It is a very weak inhibitor of nor-epinephrine (NE) uptake but it is still more potent at this site than the other SSRIs. One of the top SSRIs in terms of nor-epinephrine to serotonin (NE5-HT) absorption inhibitory inhibition selectivity is paroxetine. Comparatively to tricyclic antidepressants (TCAs), paroxetine has a lower propensity to have adverse effects on the central and autonomic nervous systems since it has limited affinity for the catecholaminergic, dopaminergic, or histaminergic systems. Compared to TCAs, paroxetine has substantially lower muscarinic cholinergic receptor affinity. Additionally, paroxetine causes adaptive alterations in somatodendritic (5-HT1A) and terminal (5-HT1B1D) autoreceptors that are distinct from those caused by TCAs. It also inhibits nitric oxide synthase. It is a cytochrome isoenzyme P450 2D6 substrate as well as an inhibitor. The first pass metabolism of paroxetine is substantial and partially saturable when taken orally.Its metabolites are inactive pharmacologically in vivo. After 4 to 14 days, steady state levels are attained, and a half-life of 21 hours for elimination is consistent with once-daily dosing. Adults, children, and the elderly all exhibit significant inter-individual variation in the pharmacokinetics of paroxetine, with the latter showing higher plasma concentrations and slower clearance. Severe renal and hepatic dysfunction also results in decreased elimination. Even in overdose, however, serious adverse outcomes are quite uncommon. Overall, paroxetine is safe and effective for treating both anxiety and depressive disorders across the age spectrum.