Switching from Duloxetine 120mg to Mirtazapine: Recommended Regimen
When switching from duloxetine 120mg daily to mirtazapine, a gradual cross-tapering approach is recommended to minimize withdrawal symptoms and maintain therapeutic efficacy.
Rationale for Switch
- Mirtazapine is a potent and well-tolerated antidepressant that promotes sleep, appetite, and weight gain, making it particularly useful for patients with insomnia and poor appetite 1
- Mirtazapine differs from duloxetine by not being a reuptake inhibitor; instead, it enhances noradrenergic neurotransmission through alpha2-autoreceptor blockade 2
Recommended Switching Protocol
Week 1:
- Reduce duloxetine from 120mg to 90mg daily
- Start mirtazapine 15mg at bedtime 3
- Monitor for serotonin syndrome or withdrawal symptoms 4
Week 2:
- Further reduce duloxetine to 60mg daily
- Increase mirtazapine to 30mg at bedtime if tolerated and clinically indicated 3
Week 3:
- Reduce duloxetine to 30mg daily
- Maintain mirtazapine at 30mg at bedtime (or increase to 45mg if needed and tolerated) 1
Week 4:
- Discontinue duloxetine completely
- Continue mirtazapine at optimal dose (30-45mg at bedtime) 3
Important Considerations
Potential Withdrawal Symptoms
- Abrupt discontinuation of duloxetine can cause withdrawal symptoms including dizziness, nausea, headache, paresthesia, irritability, and nightmares 1
- Abrupt discontinuation of mirtazapine has been associated with panic attacks and anxiety symptoms 5
Monitoring Parameters
- Monitor for serotonin syndrome during cross-tapering (symptoms include agitation, hallucinations, rapid heart rate, fever, excessive sweating, shivering, tremor, muscle stiffness, coordination problems) 1
- Assess sleep quality, as mirtazapine is more sedating than duloxetine 6
- Monitor for common side effects of mirtazapine including somnolence, increased appetite, weight gain, and dry mouth 1
Dosage Adjustments
- The recommended starting dose of mirtazapine is 15mg once daily at bedtime 3
- Dose can be increased to a maximum of 45mg per day based on response 3
- Allow 1-2 weeks between dose changes to properly evaluate response 3
Special Considerations
- If insomnia is a prominent symptom, mirtazapine may be particularly beneficial due to its sedating properties 1
- Mirtazapine is contraindicated with MAOIs; ensure at least 14 days between stopping mirtazapine and starting an MAOI 3
- Consider drug interactions: strong CYP3A inducers or inhibitors may require dosage adjustments of mirtazapine 3
Advantages of This Approach
- Cross-tapering minimizes the risk of discontinuation symptoms 4
- The gradual approach allows time to assess tolerability of mirtazapine while maintaining antidepressant coverage 7
- Evening dosing of mirtazapine capitalizes on its sedating effects to improve sleep 1
This regimen balances the need to minimize withdrawal symptoms while transitioning to an effective alternative medication with a different mechanism of action.