What is the proper dosing and administration of Paxil (paroxetine)?

Paroxetine (Paxil) Dosing and Administration Guidelines

The recommended initial dose of paroxetine is 20 mg once daily, administered in the morning with or without food, with dose adjustments made at intervals of at least one week based on clinical response and tolerability. 1

Initial Dosing by Indication

Major Depressive Disorder

• Initial dose: 20 mg/day
• Dose range: 20-50 mg/day
• Maximum dose: 50 mg/day
• Dose adjustments: Increase in 10 mg increments at intervals of at least 1 week 1

Obsessive-Compulsive Disorder

• Initial dose: 20 mg/day
• Target dose: 40 mg/day
• Dose range: 20-60 mg/day
• Maximum dose: 60 mg/day
• Dose adjustments: Increase in 10 mg increments at intervals of at least 1 week 1

Panic Disorder

• Initial dose: 10 mg/day
• Target dose: 40 mg/day
• Dose range: 10-60 mg/day
• Maximum dose: 60 mg/day
• Dose adjustments: Increase in 10 mg increments at intervals of at least 1 week 1

Social Anxiety Disorder

• Initial and recommended dose: 20 mg/day
• Dose range: 20-60 mg/day (no additional benefit observed above 20 mg/day) 1

Generalized Anxiety Disorder

• Initial and recommended dose: 20 mg/day
• Dose range: 20-50 mg/day
• Dose adjustments: Increase in 10 mg increments at intervals of at least 1 week 1

Post-Traumatic Stress Disorder

• Initial and recommended dose: 20 mg/day
• Dose range: 20-50 mg/day
• Dose adjustments: Increase in 10 mg increments at intervals of at least 1 week 1

Special Populations

Elderly, Debilitated Patients, and Patients with Severe Renal or Hepatic Impairment

• Initial dose: 10 mg/day
• Maximum dose: 40 mg/day
• Increase dose if indicated based on clinical response 1

Pregnant Women (Third Trimester)

• Consider tapering paroxetine in the third trimester due to risk of neonatal complications 1
• Neonatal complications may include irritability, jitteriness, feeding difficulties, respiratory distress, and seizures 2

Administration Considerations

• Administer as a single daily dose, usually in the morning 1, 3
• May be taken with or without food 1
• For most patients, 20 mg/day will be the optimal dose 3
• Full therapeutic effect may be delayed; allow 1-3 weeks before considering dose increases 3

Drug Interactions and Precautions

Monoamine Oxidase Inhibitors (MAOIs)

• Allow at least 14 days between discontinuation of an MAOI and initiation of paroxetine
• Allow at least 14 days after stopping paroxetine before starting an MAOI 1
• Do not start paroxetine in patients being treated with linezolid or methylene blue due to risk of serotonin syndrome 1

CYP2D6 Interactions

• Paroxetine is a strong CYP2D6 inhibitor, which requires careful monitoring when used with other medications 2
• Avoid in patients taking tamoxifen due to reduced effectiveness of tamoxifen 2

Side Effect Management

• Common side effects include nausea, decreased appetite, constipation, dry mouth, somnolence, dizziness, headache, tremor, and sexual dysfunction 2, 4
• Gastrointestinal disturbances can be managed by taking medication with food 2
• Sexual dysfunction may be managed with dose reduction 2
• Monitor for serotonin syndrome, particularly when combined with other serotonergic medications 2

Maintenance Therapy

• For major depressive disorder: Efficacy maintained for up to 1 year with average doses of about 30 mg 1
• For OCD and panic disorder: Long-term maintenance efficacy demonstrated in relapse prevention trials 1
• For all indications: Periodically reassess patients to determine need for continued treatment 1
• Maintain patients on the lowest effective dosage 1

Common Pitfalls to Avoid

1. Abrupt discontinuation can lead to withdrawal syndrome - taper gradually when stopping treatment 2
2. Starting with too high a dose, especially in elderly or those with hepatic/renal impairment
3. Increasing doses too rapidly (wait at least 1 week between dose adjustments) 1
4. Failure to monitor for drug interactions, especially with CYP2D6 substrates 2
5. Not warning patients about potential sexual side effects
6. Using in combination with MAOIs, which can lead to serotonin syndrome 1

Paroxetine is generally well tolerated with a safety profile similar to other SSRIs, making it an appropriate first-line option for its approved indications 4.