Direct Switch from Citalopram 10mg to Escitalopram 5mg
For a patient on citalopram 10mg, switch directly to escitalopram 5mg without tapering or washout period. Escitalopram is the active S-enantiomer of citalopram, making this a straightforward conversion with minimal risk of adverse effects or withdrawal symptoms 1, 2.
Dose Conversion Rationale
Escitalopram 5mg is approximately equivalent to citalopram 10mg because escitalopram contains only the therapeutically active S-isomer, while citalopram is a 50:50 racemic mixture 1, 2.
The R-enantiomer in citalopram is approximately 30-fold less potent at the serotonin transporter than the S-enantiomer, meaning half of the citalopram dose provides minimal therapeutic benefit 1.
Clinical trials demonstrate that escitalopram 10mg shows comparable or superior efficacy to citalopram 40mg, supporting a roughly 2:1 dose conversion ratio 2, 3.
Switching Method
Perform an immediate direct switch (stop citalopram 10mg today, start escitalopram 5mg tomorrow):
No tapering of citalopram is required at this low dose 4.
No washout period is necessary because both medications have the same mechanism of action and escitalopram is simply the active component already present in citalopram 1.
Both medications have similar half-lives (citalopram ~35 hours, escitalopram 27-32 hours), minimizing discontinuation risk 1.
Monitoring and Follow-up
Contact the patient within 1 week (telephone or in-person) to assess tolerability and adherence 5.
Monitor for any discontinuation symptoms, though these are unlikely given the pharmacological similarity and the fact that escitalopram maintains serotonergic activity 4.
Assess response at 4 weeks; if inadequate, consider increasing to escitalopram 10mg (equivalent to citalopram 20mg) 5, 3.
Common Pitfalls to Avoid
Do not use a 1:1 dose conversion (citalopram 10mg to escitalopram 10mg), as this would represent dose escalation and increase the risk of side effects 2, 3.
Do not perform a gradual cross-taper, as this unnecessarily prolongs the switch and provides no benefit when transitioning between these pharmacologically related medications 4.
Escitalopram has negligible effects on cytochrome P450 enzymes and lower drug interaction potential than citalopram, but continue to monitor for serotonin syndrome if the patient is on other serotonergic medications 5, 1.
Expected Outcomes
Escitalopram demonstrates earlier separation from placebo (within 1 week) compared to citalopram (4-6 weeks), so the patient may experience faster symptom improvement 2.
The most common adverse effects with escitalopram include nausea (>10%), insomnia, diarrhea, and dry mouth, though the 10mg dose shows similar discontinuation rates to placebo 1, 3.
At the 5mg starting dose, tolerability should be excellent with minimal new side effects 3.