paroxetin

Paroxetin (paroxetine) is an antidepressant in the selective serotonin reuptake inhibitor (SSRI) class. It is prescribed for major depressive disorder and a range of anxiety and related conditions, including generalized anxiety disorder, social anxiety disorder, panic disorder, obsessive-compulsive disorder, post-traumatic stress disorder, and premenstrual dysphoric disorder. It may be used when patients do not respond to other treatments.

Mechanism and properties: Paroxetin inhibits the serotonin transporter (SERT), increasing serotonin levels in the synaptic cleft. Like other SSRIs, therapeutic effects typically emerge after several weeks. Compared with some other SSRIs, paroxetin has relatively strong anticholinergic activity, which can contribute to certain adverse effects.

Pharmacokinetics: The drug is taken orally. It reaches peak plasma concentrations within a few hours; the elimination half-life is roughly one day, though this can vary. It is extensively metabolized in the liver, mainly by the CYP2D6 enzyme; genetic differences and drug interactions can alter exposure. It is excreted in urine and feces.

Side effects and safety: Common adverse effects include nausea, dry mouth, sleep disturbance or sedation, sexual dysfunction, and dizziness. Paroxetin carries a relatively high risk of withdrawal symptoms if the medicine is stopped abruptly, due to its pharmacokinetic properties. Hyponatremia can occur, especially in older adults. It carries safety concerns in pregnancy and breastfeeding; use during pregnancy is generally avoided because of potential fetal harm. Serotonin syndrome can occur with other serotonergic medicines. It should not be used with monoamine oxidase inhibitors.

Interactions: Paroxetin inhibits CYP2D6 and can interact with drugs metabolized by this enzyme, such as certain antidepressants and tamoxifen, potentially reducing their effectiveness or increasing adverse effects.

History and availability: Paroxetin has been marketed under brand names including Paxil, Pexeva, and Seroxat. It is available as a branded medication and as a generic.