Can I switch from Luvox (fluvoxamine) to Prozac (fluoxetine)?

Switching from Luvox (Fluvoxamine) to Prozac (Fluoxetine)

Yes, you can switch from Luvox to Prozac, but this transition requires careful management due to fluvoxamine's association with discontinuation syndrome and its extensive drug interaction profile, particularly its potent inhibition of multiple cytochrome P450 enzymes that differ from fluoxetine's effects. 1

Key Considerations for the Switch

Discontinuation Syndrome Risk

• Fluvoxamine is specifically associated with discontinuation syndrome, characterized by dizziness, fatigue, nausea, vomiting, insomnia, vertigo, sensory disturbances, paresthesias, anxiety, and agitation. 1
• This syndrome occurs more prominently with fluvoxamine compared to longer half-life SSRIs like fluoxetine. 1
• All SSRIs should be slowly tapered when discontinued to minimize withdrawal effects. 1

Pharmacokinetic Differences Matter

• Fluvoxamine has greater potential for drug-drug interactions than other SSRIs, inhibiting CYP1A2, CYP2C19, CYP2C9, CYP3A4, and CYP2D6. 1
• Fluoxetine primarily interacts with drugs metabolized by CYP2D6 and has a very long half-life. 1
• Fluoxetine's activating properties and extended half-life (meaning side effects may not manifest for weeks) require different monitoring than fluvoxamine. 1

Recommended Switching Strategy

Tapering Approach

• Taper fluvoxamine over 10 to 14 days to limit withdrawal symptoms, rather than abrupt discontinuation. 1
• Given fluvoxamine's shorter half-life compared to fluoxetine, a conservative taper is essential to avoid discontinuation syndrome. 1

Initiating Fluoxetine

• Start fluoxetine at a low dose (10 mg every other morning initially) due to its activating properties and very long half-life. 1
• When combining or switching between serotonergic drugs, start the second drug at a low dose, increase slowly, and monitor for symptoms especially in the first 24 to 48 hours after dosage changes to avoid serotonin syndrome. 1
• Fluoxetine can be titrated at approximately 3- to 4-week intervals (longer than shorter half-life SSRIs) until optimal benefit is achieved. 1

Critical Safety Monitoring

• Monitor closely for serotonin syndrome during the transition, which can arise within 24 to 48 hours and presents with mental status changes, neuromuscular hyperactivity (tremors, clonus, hyperreflexia), and autonomic hyperactivity (hypertension, tachycardia, diaphoresis). 1
• Watch for emergence of anxiety or agitation as an initial adverse effect of fluoxetine, which may require starting with a subtherapeutic "test" dose. 1
• Contact (in-person or telephone) should occur after initiation to review adherence, current status, and monitor for adverse events. 1

Common Pitfalls to Avoid

• Do not abruptly stop fluvoxamine without tapering, as this significantly increases discontinuation syndrome risk. 1
• Do not start fluoxetine at higher doses, as this increases the risk of behavioral activation and suicide-related events. 1
• Do not overlook drug interactions: If the patient is on medications metabolized by CYP1A2 (affected by fluvoxamine but not fluoxetine), dosage adjustments may be needed as fluvoxamine is discontinued. 1
• Do not assume immediate effect: Fluoxetine's very long half-life means side effects and therapeutic effects may not manifest for several weeks. 1