Starting Paxil (Paroxetine): Dosing and Titration Guide
Initial Dosing by Indication
For major depressive disorder, start paroxetine at 20 mg once daily in the morning, taken with or without food. 1 This is both the recommended starting dose and the minimum effective dose for depression. 1, 2
For panic disorder, start at 10 mg once daily in the morning, with a target dose of 40 mg/day. 1 The lower starting dose for panic disorder is critical because patients with panic disorder may experience initial anxiety activation with higher starting doses. 3
For obsessive-compulsive disorder (OCD), start at 20 mg once daily, with a target therapeutic dose of 40 mg/day. 1 The therapeutic range for OCD extends from 20-60 mg/day, with 40 mg/day being the recommended target. 1
For social anxiety disorder, generalized anxiety disorder, and PTSD, start at 20 mg once daily in the morning. 1 This is both the starting and established effective dose for these conditions. 1
Titration Schedule
Increase the dose in 10 mg increments at intervals of at least 1 week if the initial dose is insufficient. 1, 2 This weekly interval is essential to allow steady-state plasma concentrations to be achieved, which takes 7-14 days due to paroxetine's 24-hour half-life and saturable first-pass metabolism. 4
The maximum dose is 50 mg/day for depression and 60 mg/day for anxiety disorders (OCD, panic disorder, social anxiety disorder). 1 For most patients with depression, 20 mg/day will be the optimal dose, and only those not responding adequately should have doses increased. 1, 2
Special Populations
For elderly patients, debilitated patients, or those with severe renal or hepatic impairment, start at 10 mg once daily and do not exceed 40 mg/day. 1 These populations have higher plasma concentrations and slower elimination of paroxetine. 4
Timing and Administration
Administer as a single daily dose, usually in the morning, with or without food. 1 The 24-hour elimination half-life supports once-daily dosing. 4
Monitoring Timeline
Assess response after 1-3 weeks of treatment at the initial dose before considering dose escalation. 2 For depression, the full therapeutic effect may be delayed, which is consistent with the adaptive changes in serotonergic autoreceptors that occur with repeated administration. 3, 4
Continue monitoring monthly until symptoms are stabilized, then periodically reassess the need for continued treatment. 1 Long-term maintenance has been demonstrated effective for up to 1 year in depression and 6 months to 1 year in anxiety disorders. 5, 6
Common Pitfalls to Avoid
Do not increase doses more frequently than weekly intervals. 1 Paroxetine exhibits saturable metabolism and nonlinear pharmacokinetics with dose increases, requiring adequate time between adjustments. 4
Do not start at 20 mg in patients with panic disorder. 1 The 10 mg starting dose is specifically recommended to minimize initial anxiety activation. 3
Do not combine with MAOIs or start within 14 days of MAOI discontinuation due to serotonin syndrome risk. 1 Similarly, allow at least 14 days after stopping paroxetine before starting an MAOI. 1
Expected Adverse Effects
Counsel patients about common side effects: nausea (most common), sexual dysfunction, somnolence, headache, dry mouth, constipation, dizziness, sweating, and tremor. 5, 6, 3 These are generally mild and often diminish with continued treatment. 5
Paroxetine is generally better tolerated than tricyclic antidepressants and has a similar tolerability profile to other SSRIs. 5, 6 It is safer in overdose than tricyclics and lacks the dependence potential of benzodiazepines. 3