Paroxetine is a selective serotonin reuptake inhibitor (SSRI) used in the therapy of depression, anxiety disorders and obsessive-compulsive disorder. Paroxetine therapy can be associated with transient asymptomatic elevations in serum aminotransferase levels and has been linked to rare instances of clinically apparent acute liver injury.
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.
Mechanism of Action of Paroxetine
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. 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.
Indications of Paroxetine
- Anxiety
- Anxiety and stress
- Body dysmorphic disorder
- Depression
- Postmenopausal symptoms
- Generalized anxiety disorder
- Intermittent explosive disorder
- Major depressive disorder
- Obsessive compulsive disorder
- Panic disorder
- Persistent depressive disorder
- Post traumatic stress disorder
- Postpartum depression
- Premenstrual dysphoric disorder
- Social anxiety disorder
- Somatoform pain disorder
- Trichotillomania
- Irritable bowel syndrome
- Vasomotor Symptoms
Contra-Indications of Paroxetine
- Syndrome of Inappropriate Antidiuretic Hormone Secretion
- low amount of sodium in the blood
- increased risk of bleeding
- Behaving with Excessive Cheerfulness and Activity
- Manic-Depression
- Having Thoughts of Suicide
- serotonin syndrome – adverse drug interaction
- closed angle glaucoma
- liver problems
- Bleeding from Stomach
- Esophagus or Duodenum
- severe renal impairment
- seizures
- A Feeling of Restlessness with Inability to Sit Still
- pregnancy
- Broken Bone due to Disease or Illness
- risk of angle-closure glaucoma due to narrow angle of anterior chamber of eye
Dosage of Paroxetine
Strengths: 12.5 mg; 25 mg; 37.5 mg; 10 mg; 20 mg; 30 mg; 40 mg; 10 mg/5 mL; 7.5 mg; mesylate 10 mg; mesylate 20 mg; mesylate 30 mg; mesylate 40 mg
Depression
Immediate-release tablets and suspension
- Initial dose: 20 mg orally once a day
- Maintenance dose: 20 to 50 mg orally once a day
- Maximum dose: 50 mg orally once a day
Controlled-release tablets
- Initial dose: 25 mg orally once a day
- Maintenance dose: 25 to 62.5 mg orally once a day
- Maximum dose: 62.5 mg orally once a day.
Social Anxiety Disorder
Immediate-release tablets and suspension
- Initial dose: 20 mg orally once a day
- Maintenance dose: 20 to 60 mg orally once a day
- Maximum dose: 60 mg orally once a day
Controlled-release tablets
- Initial dose: 12.5 mg orally once a day
- Maintenance dose: 12.5 to 37.5 mg orally once a day
Panic Disorder
Immediate-release tablets and suspension
- Initial dose: 10 mg orally once a day
- Maintenance dose: 10 to 40 mg orally once a day
- Maximum dose: 60 mg orally once a day
Controlled-release oral tablets
- Initial dose: 12.5 mg orally once a day
- Maintenance dose: 12.5 to 75 mg orally once a day
- Maximum dose: 75 mg orally once a day
Premenstrual Dysphoric Disorder
Controlled-release tablets
Continuous regimen
- Initial dose: 12.5 mg orally once a day during the menstrual cycle
- Maintenance dose: 25 mg orally once a day during the menstrual cycle
Cyclic regimen
- Initial dose: 12.5 mg orally once a day, starting 14 days prior to the anticipated start of menstruation through to the first full day of menses, and repeated with each new cycle
- Maintenance dose: 12.5 to 25 mg orally once a day
Obsessive Compulsive Disorder
Immediate-release tablets and suspension
- Initial dose: 20 mg orally once a day
- Maintenance dose: 20 to 60 mg orally once a day
- Maximum dose: 60 mg orally once a day
Duration: Efficacy has been demonstrated for up to 6 months
Generalized Anxiety Disorder
Immediate-release tablets and suspension
- Initial dose: 20 mg orally once a day
- Maintenance dose: 20 to 50 mg orally once a day
- Maximum dose: 50 mg orally once a day
Geriatric Dose for Depression
Immediate-release tablets and suspension
- Initial dose: 10 mg orally once a day
- Maintenance dose: 10 to 40 mg orally once a day
- Maximum dose: 40 mg orally once a day
Controlled-release tablets
- Initial dose: 12.5 mg orally once a day
- Maintenance dose: 12.5 to 50 mg orally once a day
- Maximum dose: 50 mg orally once a day
Side Effects of Paroxetine
The most common
- clumsiness or unsteadiness
- dizziness
- drowsiness
- dry mouth
- false sense of well-being
- increased watering of mouth
- lightheadedness
- constipation;
- vision changes;
- breast swelling (in men or women); or
- decreased sex drive, impotence, or difficulty having an orgasm.
- blurred vision, tunnel vision, eye pain or swelling, or seeing halos around lights;
- restless muscle movements in your eyes, tongue, jaw, or neck;
- a light-headed feeling, like you might pass out;
Common
- Drowsiness and lightheadedness the day after taking the medicine.
- Confusion.
- Numbed emotions.
- Visual disturbances such as blurred vision or double vision.
- Shaky movements and unsteady walk (ataxia).
- Loss of memory (amnesia).
- Muscle weakness.
- Dizziness.
- Headache.
- Skin rashes.
- Disturbances of the gut such as diarrhoea, constipation, nausea, vomiting or abdominal pain.
- Difficulty in passing urine (urinary retention).
- Changes in sex drive.
- Low blood pressure (hypotension).
- Blood disorders.
- Jaundice.
- Unexpected aggression, restlessness or irritability (tell your doctor if you experience this).
- Nightmares or hallucinations (tell your doctor if you experience this).
Serious
- agitation
- anxiety
- behavioural changes, including aggressiveness, angry outbursts, bizarre behaviour, or decreased inhibitions
- confusion
- increased trouble sleeping
- memory problems
- muscle spasms
- shortness of breath
- signs of depression (e.g., poor concentration, changes in weight, changes in sleep, decreased interest in activities, thoughts of suicide)
- sleepwalking
Drug Interactions of Paroxetine
Paroxetine may interact with following drugs, supplements & may change the efficacy of drugs
- amlodipine
- general anesthetics
- antihistamines (e.g., cetirizine, doxylamine, diphenhydramine, hydroxyzine, loratadine)
- antipsychotics (e.g., chlorpromazine, clozapine, haloperidol, olanzapine, quetiapine, risperidone)
- aripiprazole
- baclofen
- barbiturates (e.g., butalbital, pentobarbital, phenobarbital)
- benzodiazepines (e.g., alprazolam, diazepam, lorazepam)
- bupropion
- celecoxib
- cilostazol
- clopidogrel
- cyclosporine
- diabetes medications (e.g., chlorpropamide, metformin, nateglinide, rosiglitazone)
- diltiazem
- estrogens (e.g., conjugated estrogen, )
- glucosamine
- heparin
- low molecular weight heparins
- mirtazapine
- monoamine oxidase inhibitors (MAOIs; e.g. rasagiline, selegiline, )
- multivitamins
- muscle relaxants
- nifedipine
- non-steroidal anti-inflammatory medications (NSAIDs; e.g., diclofenac, ibuprofen, naproxen)
- omega-3 fatty acids
- pentoxifylline
- propranolol
- quinolone antibiotics (e.g., ciprofloxacin, norfloxacin, ofloxacin)
- rasagiline
- seizure medications ( phenobarbital, phenytoin, valproic acid, )
- selective serotonin reuptake inhibitors (SSRIs; e.g., citalopram, duloxetine, fluoxetine, paroxetine, sertraline)
- serotonin antagonists (anti-emetic medications; e.g., granisetron, ondansetron)
- tapentadol
- theophyllines (e.g., aminophylline, oxtriphylline, theophylline)
- thiazide diuretics (water pills; e.g., hydrochlorothiazide, )
- thyroid replacements (e.g., dessicated thyroid, levothyroxine)
- tizanidine
- tramadol
- tricyclic antidepressants (e.g., desipramine, nortriptyline)
- triptans (e.g., sumatriptan, rizatriptan)
Pregnancy & Lactation of Paroxetine
Pregnancy
Pregnant women should not take paroxetine, particularly in early pregnancy and during the last few months of pregnancy. The drug may cause heart defects in unborn babies and has been linked to other health problems in newborns.
Lactation
If you’re breastfeeding a baby, talk with your doctor before taking paroxetine because the drug may affect the quality of your breast milk.
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