What is the normal adult dose of paroxetine extended‑release?

Normal Dose of Paroxetine Extended-Release

For paroxetine extended-release (ER), start at 12.5 mg once daily and increase to 25 mg daily after one week if greater symptom control is needed; the therapeutic range is 12.5–25 mg/day for most indications, with no significant efficacy difference between these doses. 1

Standard Dosing for Paroxetine ER

• Initial dose: 12.5 mg once daily 1
• Target dose: 25 mg once daily after 1 week 1
• Therapeutic range: 12.5–25 mg/day 1

The evidence from controlled trials demonstrates that both 12.5 mg and 25 mg doses produce clinically significant reductions in symptoms (62% and 65% composite hot flash score reductions respectively), with no statistically significant differences in efficacy between the two dose levels. 1

Comparison with Immediate-Release Paroxetine

For context, immediate-release paroxetine follows a different dosing paradigm:

• Starting dose: 20 mg once daily (also the minimal effective dose) 2
• Therapeutic range: 20–50 mg/day 3, 4
• Dose escalation: Increase in 10 mg increments at weekly intervals if inadequate response after 1–3 weeks 2
• Maximum dose: 50 mg/day 3, 4, 2
• Elderly patients: 20–40 mg/day 2

Timing and Administration

• Administer as a single daily dose 2
• Morning dosing is typically preferred 2
• Take with or without food (not specified in guidelines, but standard SSRI practice)

Dose Escalation Strategy for ER Formulation

If starting at 12.5 mg daily:

1. Week 1: Begin 12.5 mg once daily 1
2. Week 2 onward: Increase to 25 mg once daily if greater symptom control is desired 1
3. Do not exceed 25 mg/day for the ER formulation in the studied population 1

Common Adverse Effects to Monitor

• Nausea (most common, dose-related) 1, 3, 4, 5
• Dizziness 1, 3, 4, 5
• Insomnia 1, 3, 4
• Sexual dysfunction 3, 4, 5
• Somnolence 3, 4, 5
• Headache 3, 4, 5
• Constipation 3, 4, 5
• Sweating 3, 4, 5

Notably, nausea was significantly increased at the 25 mg dose compared to 12.5 mg in controlled trials, and a greater percentage of patients discontinued the higher dose due to adverse effects. 1

Critical Drug Interaction Warning

Paroxetine is a potent CYP2D6 inhibitor and should not be combined with tamoxifen, as it significantly reduces plasma levels of endoxifen (the active metabolite of tamoxifen), potentially compromising cancer treatment efficacy. 1 This interaction is particularly relevant given that paroxetine ER has been studied for hot flash management in women who may be taking tamoxifen.

Important Clinical Caveats

• Discontinuation syndrome risk: Paroxetine is associated with withdrawal symptoms; never stop abruptly—taper gradually over a minimum of 2–4 weeks 6
• Onset of effect: Most adverse effects emerge within the first few weeks of treatment 6
• Bioavailability: Paroxetine undergoes partially saturated first-pass metabolism, reducing bioavailability to approximately 30–60% at therapeutic doses 7
• Protein binding: 95% plasma protein-bound 7
• Peak levels: Reached 2–8 hours after oral administration 7

When to Consider Dose Adjustment

• Inadequate response after 1 week at 12.5 mg: Increase to 25 mg daily 1
• Intolerable nausea at 25 mg: Consider reducing back to 12.5 mg, as efficacy is similar 1
• Elderly patients or hepatic impairment: Use lower end of dosing range and monitor closely 2