Cross-Tapering from Luvox (Fluvoxamine) to Cymbalta (Duloxetine)
Immediately switch from fluvoxamine to duloxetine 60 mg once daily without tapering fluvoxamine, as this approach is well-tolerated and avoids the significant drug interaction between these medications. 1
Critical Drug Interaction Warning
- Fluvoxamine is a potent CYP1A2 inhibitor that increases duloxetine exposure by 460% and bioavailability from 43% to 82% 2
- Coadministration of duloxetine with potent CYP1A2 inhibitors like fluvoxamine should be avoided 2
- Any overlap period during cross-tapering would create dangerous drug accumulation and increased adverse effects 2
Recommended Switching Protocol
Week 1: Immediate Switch
- Discontinue fluvoxamine completely on day 1 1
- Start duloxetine 60 mg once daily on day 1 1
- Take duloxetine with food to minimize nausea 3
- No tapering of fluvoxamine is required before switching 1
Rationale for Immediate Switch
- Direct switching from SSRIs (including fluvoxamine) to duloxetine 60 mg daily without intermediate tapering was associated with significantly lower discontinuation rates due to adverse events (6.3%) compared to initiating duloxetine in untreated patients (16.1%) 1
- Patients switched directly to duloxetine reported significantly lower rates of headache and fatigue in the first week compared to those initiating duloxetine 1
- The immediate switch approach was well-tolerated and achieved comparable efficacy to initiating duloxetine in untreated patients 1
Dosing Strategy to Minimize Side Effects
Initial Week
- Start duloxetine at 60 mg once daily in the morning with food 3
- Taking duloxetine with food significantly reduces nausea, particularly when starting at the therapeutic dose of 60 mg 3
- The food-by-dose interaction showed the greatest benefit from taking drug with food occurred in patients started at 60 mg 3
Weeks 2-6
- Continue duloxetine 60 mg once daily 1
- This dose is effective for the majority of patients with major depressive disorder 4
- Monitor for response and tolerability 1
Dose Adjustment if Needed
- If inadequate response after 2-4 weeks at 60 mg, may increase to 90 mg once daily 4
- If still inadequate, may further increase to 120 mg once daily 4
- Rapid weekly dose escalation (60→90→120 mg) is safe and tolerable, with most adverse events occurring during the first week at 60 mg 4
Monitoring for Withdrawal Symptoms
Fluvoxamine Discontinuation
- Monitor for SSRI discontinuation syndrome symptoms including: 5
- The immediate switch to duloxetine (another serotonergic agent) typically prevents withdrawal symptoms 1
Common Side Effects During Transition
- Nausea is the most common adverse event (occurs in 23-29% of patients starting duloxetine) 3
- Other frequent side effects include headache, dry mouth, dizziness, and decreased appetite 4
- Most adverse events are mild, transient, and occur in the first week of duloxetine dosing 4
Special Monitoring Considerations
Cardiovascular Monitoring
- Monitor blood pressure, as duloxetine can cause modest increases (mean 3.8 mmHg systolic) 4
- Monitor heart rate (mean increase of 5.9 bpm over long-term treatment) 4
- For patients with cardiac disease, closer monitoring is warranted 5
Weight Monitoring
- Expect modest weight gain (mean 3.1 kg over 2 years of treatment) 4
Common Pitfalls to Avoid
- Never attempt a gradual cross-taper with overlapping doses due to the severe CYP1A2 interaction between fluvoxamine and duloxetine 2
- Never start duloxetine at doses lower than 60 mg when switching from another antidepressant, as this provides no tolerability advantage and delays therapeutic effect 1
- Never take duloxetine without food when starting at 60 mg, as this significantly increases nausea and discontinuation rates 3
- Failing to monitor for the drug interaction can lead to duloxetine toxicity if any overlap occurs 2