SEROXAT TABLET 20mg FOR ORAL USE

Product Information

Registration Status: Active

SEROXAT TABLET 20mg is approved to be sold in Singapore with effective from 1992-09-06. It is marketed by GLAXOSMITHKLINE PTE LTD, with the registration number of SIN07053P.

This product contains Paroxetine 20mg in the form of TABLET, FILM-COATED. It is approved for ORAL use.

This product is manufactured by GlaxoSmithKline Pharmaceuticals S.A. in POLAND.

It is a Prescription Only Medicine that can only be obtained from a doctor or a dentist, or a pharmacist with a prescription from a Singapore-registered doctor or dentist.

Description

Paroxetine hydrochloride and paroxetine mesylate belong to a class of antidepressant agents known as selective serotonin-reuptake inhibitors (SSRIs). Despite distinct structural differences between compounds in this class, SSRIs possess similar pharmacological activity. As with other antidepressant agents, several weeks of therapy may be required before a clinical effect is seen. SSRIs are potent inhibitors of neuronal serotonin reuptake. They have little to no effect on norepinephrine or dopamine reuptake and do not antagonize ⍺- or β-adrenergic, dopamine D₂ or histamine H₁ receptors. During acute use, SSRIs block serotonin reuptake and increase serotonin stimulation of somatodendritic 5-HT_1A and terminal autoreceptors. Chronic use leads to desensitization of somatodendritic 5-HT_1A and terminal autoreceptors. The overall clinical effect of increased mood and decreased anxiety is thought to be due to adaptive changes in neuronal function that leads to enhanced serotonergic neurotransmission. Side effects include dry mouth, nausea, dizziness, drowsiness, sexual dysfunction and headache (see Toxicity section below for a complete listing of side effects). 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. Clinical studies establishing the efficacy of paroxetine in various conditions were performed using paroxetine hydrochloride. Since both agents contain the same active moiety, the clinical efficacy of both agents is thought to be similar. Paroxetine may be used to treat 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). 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.

Indication

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.

Mechanism of Action

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.

Pharmacokinetics

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. Absorption of either salt form is not substantially affected by food. Peak concentrations of Brisbelle (mesylate salt) were reached at 6 hours (3 to 8 hours range). Steady state Cmax was 13.10 ng/mL. The steady state AUC (0-last) was 237 hr*ng/mL. Paroxetine mesylate generally follows non-linear pharmacokinetics because CYP2D6, the enzyme that is part responisible for paroxetine metabolism, is readily saturable.
Distribution: 3.1-28 L/kg observed in animal studies. Paroxetine distributes throughout the body, including the central nervous system, with only 1% remaining in the plasma.
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.
Elimination

Toxicity

LD₅₀=500mg/kg (orally in mice). Symptoms of overdose include: coma, dizziness, drowsiness, facial flushing, nausea, sweating, tremor, vomiting. Side effects include: nervous system effects such as asthenia, somnolence, dizziness, insomnia, tremor, and nervousness; GI effects such as 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. Discontinuation syndrome may occur with abrupt withdrawal. Symptoms of discontinuation syndrome include flu-like symptoms, insomnia, nausea, imbalance, sensory changes, and hyperactivity.

Active Ingredient/Synonyms

Source of information: Drugbank (External Link). Last updated on: 3^rd July 18. *Trade Name used in the content below may not be the same as the HSA-registered product.