Switching from Lexapro 10mg to Citalopram 10mg
Direct Switch is NOT Recommended – Dose Adjustment Required
A direct switch from escitalopram (Lexapro) 10mg to citalopram 10mg is not pharmacologically equivalent and will result in underdosing; you must switch to citalopram 20mg to maintain therapeutic equivalence. 1
Pharmacological Rationale
Escitalopram is the isolated S-enantiomer of citalopram and is approximately twice as potent – the therapeutic activity of citalopram resides entirely in the S-isomer, while the R-enantiomer is approximately 30-fold less potent at the serotonin transporter. 2
Escitalopram 10mg is therapeutically equivalent to citalopram 20mg, not citalopram 10mg, because citalopram is a 50:50 racemic mixture containing both the active S-enantiomer and the essentially inactive R-enantiomer. 1, 2
Switching to citalopram 10mg would deliver only half the active S-enantiomer dose the patient is currently receiving, risking symptom relapse or inadequate therapeutic coverage. 1
Recommended Switching Protocol
Make an immediate direct switch without taper or washout period – stop escitalopram 10mg and start citalopram 20mg the next day. 1
This is one of the rare exceptions where cross-tapering is unnecessary because you are essentially continuing the same active medication (S-citalopram) at an equivalent dose. 1
Both medications have similar half-lives (escitalopram 27-33 hours, citalopram comparable) and safety profiles, making direct substitution safe. 1, 3
The switch from intravenous citalopram to oral escitalopram has been demonstrated to be well tolerated with continued efficacy, supporting the safety of transitioning between these closely related medications. 4
Safety Monitoring During the Switch
Schedule follow-up contact within 1-2 weeks to assess tolerability and monitor for any emergence of adverse events or discontinuation symptoms. 1
Monitor for discontinuation symptoms (dizziness, fatigue, headaches, nausea, insomnia, anxiety) during the first 1-2 weeks, though these are unlikely given the pharmacological similarity and immediate substitution of equivalent doses. 1
Assess for suicidal ideation at every contact during the first 1-2 months after the medication change, as this risk period applies to any antidepressant regimen modification. 1
Critical Dosing Limits and Cardiac Safety
The maximum recommended dose for citalopram is 40mg daily due to dose-dependent QT interval prolongation risk at higher doses; citalopram 20mg is well within the safe therapeutic range. 1
Do not exceed citalopram 40mg daily without cardiac monitoring and ECG assessment. 1
Both medications are contraindicated with MAOIs and require caution with other serotonergic agents due to serotonin syndrome risk. 1
Common Pitfall to Avoid
Do not switch to citalopram 10mg thinking it is equivalent to escitalopram 10mg – this represents a 50% dose reduction of the active S-enantiomer and will likely result in loss of therapeutic effect or symptom recurrence. 1, 2