Paroxetine is an antidepressant in a group of drugs called selective serotonin reuptake inhibitors (SSRIs). Paroxetine affects chemicals in the brain that may be unbalanced in people with depression, anxiety, or other disorders.
Labeled indications include: major depressive disorder (MDD), panic disorder with or without agoraphobia, obsessive-compulsive disorder (OCD), social anxiety disorder (social phobia), generalized anxiety disorder (GAD), post-traumatic stress disorder (PTSD), and premenstrual dysphoric disorder (PMDD).
Unlabeled indications include: eating disorders, impulse control disorders, vasomotor symptoms of menopause, obsessive-compulsive disorder (OCD) in children, and mild dementia-associated agitation in nonpsychotic individuals. Brisdelle, which consists of paroxetine mesylate is indicated for the treatment of moderate to severe vasomotor symptoms (like hot flashes) associated with menopause.
Paroxetine, an antidepressant drug of the selective serotonin reuptake inhibitor (SSRI) type, has no active metabolites and has the highest specificity for serotonin receptors of all the SSRIs.
It is used to treat depression resistant to other antidepressants, depression complicated by anxiety, panic disorder, social and general anxiety disorder, obsessive-compulsive disorder (OCD), premenstrual dysphoric disorder, premature ejaculation, and hot flashes of menopause in women with breast cancer. In human platelets, paroxetine blocks the uptake of serotonin.
It has weak effects on norepinephrine and dopamine neuronal reuptake. In vitro radioligand binding studies indicate that paroxetine has little affinity for muscarinic alpha1-, alpha2-, beta-adrenergic-, dopamine (D2)-, 5-HT1-, 5-HT2-, and histamine (H1)-receptors.
Paroxetine is a potent and highly selective inhibitor of neuronal serotonin reuptake. Paroxetine likely inhibits the reuptake of serotonin at the neuronal membrane, enhances serotonergic neurotransmission by reducing turnover of the neurotransmitter, therefore it prolongs its activity at synaptic receptor sites and potentiates 5-HT in the CNS; paroxetine is more potent than both sertraline and fluoxetine in its ability to inhibit 5-HT reuptake.
Compared to the tricyclic antidepressants, SSRIs have dramatically decreased binding to histamine, acetylcholine, and norepinephrine receptors. The mechanism of action for the treatment of vasomotor symptoms is unknown.
Paroxetine has the most evidence supporting its use for anxiety-related disorders of the SSRIs. It has the greatest anticholinergic activity of the agents in this class and compared to other SSRIs, paroxetine may cause greater weight gain, sexual dysfunction, sedation and constipation.
Metabolism: Paroxetine is extensively metabolized after oral administration, likely in the liver. The main metabolites are polar and conjugated products of oxidation and methylation, which are readily eliminated by the body. The predominant metabolites are glucuronic acid and sulfate conjugates. Paroxetine metabolites do not possess significant pharmacologic activity (less than 2% that of parent compound). Paroxetine is metabolized by cytochrome P450 (CYP) 2D6. Enzyme saturation appears to account for the nonlinear pharmacokinetics observed with increasing dose and duration of therapy.
Absorption: Paroxetine hydrochloride is slowly, but completely absorbed following oral administration. Paroxetine mesylate salt is also completely absorbed after oral dosing. The oral bioavailability appears to be low due to extensive first-pass metabolism. Paroxetine hydrochloride oral tablets and suspension are reportedly bioequivalent.
Route of elimination: Approximately 64% of a 30 mg oral solution of paroxetine was excreted in the urine with 2% as the parent compound and 62% as metabolites. Approximately 36% of the dose was excreted in the feces (via bile), mostly as metabolites and less than 1% as parent compound.
Half life: 21-24 hours
All medicines may cause side effects, but many people have no, or minor, side effects.Some medical conditions may interact with Paroxetine.
Tell your doctor or pharmacist if you have any medical conditions.
Side effects include nausea, decreased appetite, constipation, diarrhea, and dry mouth; impotence, ejaculatory dysfunction (principally ejaculatory delay), and other male genital disorders; female genital disorders (principally anorgasmia or difficulty reaching climax/orgasm); and sweating. Side effects generally occur during the first two weeks of therapy and are usually less severe and frequent than those observed with tricyclic antidepressants. Paroxetine hydrochloride and mesylate are considered therapeutic alternatives rather than generic equivalents by the US Food and Drug Administration (FDA); both agents contain the same active moiety (i.e. paroxetine), but are formulated as different salt forms.
Discontinuation syndrome may occur with abrupt withdrawal. Symptoms of discontinuation syndrome include flu-like symptoms, insomnia, nausea, imbalance, sensory changes, and hyperactivity.
This is not a complete list of all side effects that may occur. If you have questions about side effects, contact your health care provider.
