Paroxetine

Paroxetine is a selective serotonin reuptake inhibitor (SSRI) indicated for the management of major depressive disorder, panic disorder, social anxiety disorder, generalized anxiety disorder, obsessive-compulsive disorder, and post-traumatic stress disorder. As a potent and highly specific agent, it functions by increasing serotonin activity in the central nervous system, which plays a key role in mood regulation, anxiety response, and emotional stability. Clinicians value paroxetine for its well-established efficacy, predictable pharmacokinetic profile, and versatility across multiple anxiety and mood-related conditions. Appropriate patient selection, dose titration, and monitoring are essential to maximize therapeutic outcomes and minimize adverse effects.

Features

• Active ingredient: Paroxetine hydrochloride
• Available formulations: Immediate-release tablets, controlled-release tablets, oral suspension
• Standard strengths: 10 mg, 20 mg, 30 mg, 40 mg tablets; 12.5 mg, 25 mg, 37.5 mg controlled-release
• Half-life: Approximately 21 hours (immediate-release)
• Time to peak concentration: 5–8 hours post-dose
• Protein binding: >95%
• Metabolism: Hepatic, primarily via CYP2D6
• Excretion: Renal (64%) and fecal (36%)

Benefits

• Effective reduction of depressive symptoms and restoration of functional capacity
• Significant decrease in frequency and severity of panic attacks
• Improvement in social and generalized anxiety symptoms, enhancing quality of life
• Reduction in obsessive thoughts and compulsive behaviors
• Alleviation of trauma-related symptoms including hyperarousal and avoidance
• Favorable long-term maintenance profile for chronic conditions

Common use

Paroxetine is commonly prescribed for the treatment of major depressive disorder in adults, often as a first-line pharmacological intervention. It is also widely used in the management of various anxiety disorders, including panic disorder with or without agoraphobia, social anxiety disorder, and generalized anxiety disorder. Off-label uses may include premature ejaculation, vasomotor symptoms of menopause, and certain chronic pain conditions, though evidence supporting these applications varies. Treatment should always be initiated under medical supervision with consideration of individual patient factors and comorbid conditions.

Dosage and direction

Dosage must be individualized based on diagnosis, severity of symptoms, and patient response.

• Major depressive disorder: Initial dose 20 mg once daily, preferably in the morning. May increase in 10 mg increments at intervals of at least one week. Maximum recommended dose: 50 mg/day.
• Panic disorder: Start with 10 mg/day. Increase to 20 mg/day after one week. Maximum dose: 60 mg/day.
• Social anxiety disorder: Initial dose 20 mg/day. Dose range: 20–60 mg/day.
• Generalized anxiety disorder: 20 mg/day initially. May increase to a maximum of 50 mg/day.
• Obsessive-compulsive disorder: Start with 20 mg/day. Increase gradually; maximum 60 mg/day.
• Post-traumatic stress disorder: 20 mg/day initially. Titrate as needed up to 50 mg/day.

Controlled-release formulations should be swallowed whole and not chewed or crushed. Administration with food may reduce gastrointestinal upset. Dosage adjustments are necessary in hepatic impairment, elderly patients, and those taking CYP2D6 inhibitors.

Precautions

• Monitor for worsening depression, suicidality, or unusual changes in behavior, especially during initial treatment or dose adjustments.
• Use with caution in patients with a history of mania or bipolar disorder; may precipitate manic episodes.
• May cause hyponatremia, particularly in elderly patients or those taking diuretics.
• Risk of bleeding may be increased, especially when used with NSAIDs, aspirin, or other anticoagulants.
• Discontinuation syndrome may occur upon abrupt cessation; taper gradually.
• Caution in patients with angle-closure glaucoma or history of seizures.
• Potential for serotonin syndrome, particularly when used with other serotonergic drugs.

Contraindications

• Hypersensitivity to paroxetine or any component of the formulation.
• Concurrent use with monoamine oxidase inhibitors (MAOIs) or within 14 days of discontinuing MAOI therapy.
• Use of pimozide or thioridazine concomitantly.
• Uncontrolled narrow-angle glaucoma.
• Severe hepatic impairment without appropriate dose adjustment.

Possible side effects

Common side effects (≥1/100):

• Nausea, dry mouth, constipation, diarrhea
• Drowsiness, dizziness, insomnia
• Sweating, asthenia
• Sexual dysfunction (decreased libido, anorgasmia, erectile dysfunction)

Less common side effects (<1/100):

• Weight changes (gain or loss)
• Tremor, blurred vision, yawning
• Palpitations, postural hypotension
• Urinary frequency or retention

Serious side effects (seek medical attention):

• Suicidal thoughts or behavior
• Serotonin syndrome (agitation, hallucinations, tachycardia, hyperthermia)
• Severe allergic reactions (rash, swelling, difficulty breathing)
• Abnormal bleeding or bruising
• Seizures
• Manic episodes

Drug interaction

• MAOIs: Risk of serotonin syndrome; contraindicated.
• CYP2D6 inhibitors (e.g., quinidine, fluoxetine): May increase paroxetine levels.
• Warfarin: Altered anticoagulant effect; monitor INR closely.
• Triptans, tramadol, other SSRIs/SNRIs: Increased serotonin syndrome risk.
• Drugs metabolized by CYP2D6 (e.g., tricyclic antidepressants, antipsychotics): Paroxetine may increase their concentrations.
• NSAIDs, aspirin: Increased bleeding risk.
• Pimozide, thioridazine: Contraindicated due to QT prolongation risk.

Missed dose

If a dose is missed, take it as soon as remembered unless it is close to the next scheduled dose. Do not double the dose to make up for a missed one. Maintain regular dosing schedule to ensure stable serum concentrations. Patients should be advised not to discontinue therapy abruptly due to risk of withdrawal symptoms.

Overdose

Symptoms may include nausea, vomiting, drowsiness, sinus tachycardia, dilated pupils, and agitation. Severe overdose may lead to serotonin syndrome, seizures, coma, or ECG changes including QT prolongation. There is no specific antidote; management is supportive and symptomatic. Gastric lavage or activated charcoal may be considered if presented early. Ensure adequate hydration and monitor cardiac and vital signs. Contact poison control center immediately.

Storage

Store at controlled room temperature (20–25°C or 68–77°F). Keep in original container, tightly closed, and protected from light and moisture. Do not store in bathroom or damp areas. Keep out of reach of children and pets. Do not use after expiration date. Oral suspension should not be frozen.

Disclaimer

This information is intended for educational purposes and does not replace professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before starting or changing any medication regimen. Individual response to paroxetine may vary. Not all uses, precautions, or interactions are listed here. Full prescribing information should be reviewed before administration.

Reviews

Clinical studies and meta-analyses consistently demonstrate paroxetine’s efficacy across its approved indications. In major depressive disorder, response rates typically exceed 60% with adequate dosing. Panic disorder trials show significant reduction in attack frequency compared to placebo. Long-term maintenance therapy has shown sustained benefit in preventing relapse. Tolerability profiles are generally acceptable, though side effects such as sexual dysfunction and weight gain may affect adherence in some populations. Comparative effectiveness data place paroxetine among the more potent SSRIs, particularly for anxiety spectrum disorders.