How to Switch from Citalopram 20mg to Paxil (Paroxetine)
Perform a direct switch by stopping citalopram 20mg and starting paroxetine 20mg the next day without a washout period, as this is the established minimal effective and typical starting dose for paroxetine. 1, 2
Switching Strategy
Stop citalopram 20mg and initiate paroxetine 20mg the following day as a direct switch without tapering or washout period. 1, 3
This direct switching approach between SSRIs is supported by moderate-quality evidence showing no difference in response, remission, or adverse events when transitioning between these agents. 1
Paroxetine 20mg/day is both the starting dose and the minimal effective dose, and for most patients will also be the optimal dose. 2
The medication should be given as a single daily dose, usually in the morning. 2
Discontinuation Risk Management
Citalopram has a relatively lower risk of discontinuation syndrome compared to paroxetine itself, but symptoms can still occur including dizziness, fatigue, nausea, headaches, insomnia, anxiety, and sensory disturbances. 1
Monitor closely during the first 1-2 weeks after the switch for any discontinuation symptoms from citalopram or new adverse effects from paroxetine. 3
Paroxetine has a relatively short half-life and lacks active metabolites, making it more prone to discontinuation symptoms if later stopped abruptly. 4
Dose Titration if Needed
For patients who do not show adequate therapeutic response within 1-3 weeks of initiating paroxetine 20mg, increase the dose in 10mg increments no more often than at weekly intervals to a maximum of 50mg/day. 2
Allow 6-8 weeks at therapeutic dose before declaring treatment failure. 5
Monitoring Protocol
Assess treatment response every 2-4 weeks using standardized anxiety or depression rating scales. 5
Monitor specifically for paroxetine's most common adverse events: nausea, sexual dysfunction, somnolence, asthenia, headache, constipation, dizziness, sweating, tremor, and decreased appetite. 6
Watch for suicidal ideation during the first 1-2 months after the medication change, as risk for suicide attempts is greatest during this period. 5
Expected Outcomes
No difference in antidepressant response or remission rates should be expected when switching between SSRIs like citalopram and paroxetine, based on moderate-quality evidence from randomized trials. 1
In patients who were paroxetine-intolerant and switched to citalopram, specific side effects recurred less than 30% of the time, demonstrating that SSRIs do not have interchangeable tolerability profiles. 7
Paroxetine is effective for major depressive disorder, OCD, panic disorder, social anxiety disorder, GAD, and PTSD, with efficacy similar to other SSRIs and TCAs. 6
Critical Pitfalls to Avoid
Do not use a prolonged washout period between citalopram and paroxetine, as this creates unnecessary periods without treatment and risk of symptom exacerbation. 1, 3
Do not start paroxetine at doses lower than 20mg, as this is the established minimal effective dose. 2
If later discontinuing paroxetine, gradual tapering is recommended for patients receiving more than 20mg/day to avoid marked sleep disturbances and dizziness. 4