Switching from Citalopram 10mg to Mirtazapine 7.5mg
You should NOT abruptly stop citalopram 10mg and immediately start mirtazapine 7.5mg—instead, implement a gradual cross-taper over 4-6 weeks to minimize withdrawal symptoms and serotonin syndrome risk. 1, 2
Why Abrupt Switching is Problematic
Citalopram Withdrawal Risk
- Abrupt discontinuation of citalopram can cause severe withdrawal symptoms including dizziness, nausea, myalgias, anxiety, irritability, and even sustained hypertension requiring medical intervention 3
- Discontinuing any antidepressant over 10-14 days is insufficient for patients on established therapy—this older recommendation does not adequately prevent withdrawal effects 1, 2
- Even at the low dose of 10mg, gradual tapering is essential to avoid discontinuation symptoms 1
Serotonin Syndrome Concern
- The primary safety concern when combining SSRIs with other serotonergic agents is serotonin syndrome, with symptoms typically arising within 24-48 hours of combining medications 2
- While mirtazapine has a different mechanism (alpha-2 antagonist enhancing noradrenergic and 5-HT1 serotonergic transmission), it still affects serotonergic pathways 4, 5
- Symptoms include mental status changes, neuromuscular hyperactivity (tremors, muscle twitching), autonomic hyperactivity (fever, sweating, rapid heart rate, diarrhea), and can be fatal if untreated 2
Recommended Cross-Taper Protocol
Week 1-2: Initiation Phase
- Start mirtazapine 7.5mg at bedtime while maintaining citalopram 10mg 1, 2
- Monitor intensively for serotonin syndrome symptoms in the first 24-48 hours (confusion, agitation, tremors, fever, sweating, rapid heart rate, diarrhea, muscle twitching) 2
- Maintain this combination for 7-14 days to assess tolerability 2
Week 3-4: Begin Citalopram Taper
- Reduce citalopram to 5mg daily after confirming mirtazapine tolerability 1, 2
- Continue mirtazapine 7.5mg unchanged 1
- Monitor for withdrawal symptoms (dizziness, nausea, anxiety, irritability) 3
Week 5-6: Complete Transition
- Discontinue citalopram completely after 1-2 weeks at 5mg 1, 2
- Continue mirtazapine 7.5mg at bedtime 1
- If therapeutic effect is insufficient after citalopram is fully discontinued, mirtazapine can be increased to 15mg or 30mg as needed 1, 4
Monitoring Requirements
During Cross-Taper (Weeks 1-6)
- Weekly contact (phone or in-person) is essential during the first month 2
- Instruct patient to immediately report any signs of serotonin syndrome 2
- Monitor blood pressure, as citalopram withdrawal can cause sustained hypertension 3
After Transition Complete
- Monthly follow-up until stable on mirtazapine monotherapy 2
- Note that mirtazapine's antidepressant effect may take 4-8 weeks for full therapeutic benefit 1
Critical Pitfalls to Avoid
- DO NOT abruptly stop citalopram—even at 10mg, withdrawal symptoms can be severe and include sustained hypertension 3
- DO NOT assume the low dose (10mg) makes tapering unnecessary—all SSRIs require gradual discontinuation 1, 2
- DO NOT rapidly increase mirtazapine while citalopram remains in the system—wait until citalopram is at ≤5mg or discontinued before titrating mirtazapine upward 2
- DO NOT abruptly stop mirtazapine if later discontinuation is needed—even after medium-term therapy (10 weeks), progressive tapering is advisable to avoid panic attacks and withdrawal symptoms 6
Special Considerations for Mirtazapine
Cardiovascular Safety
- Mirtazapine has been shown to be safe in patients with cardiovascular disease, with no significant cardiovascular adverse effects even at high doses 1
- Unlike citalopram/escitalopram, mirtazapine has lower risk of QTc prolongation 1
Additional Benefits
- Mirtazapine offers appetite stimulation and sleep improvement, which may be advantageous if these are treatment goals 1
- The 7.5mg dose is appropriate for initiating therapy, particularly for sleep benefits 1
- Sedation is most prominent at lower doses and may decrease as dose increases 7