fluvoxamine

General Information

Fluvoxamine (brand Luvox) is a selective serotonin reuptake inhibitor approved for obsessive-compulsive disorder (1994) and social anxiety disorder (2008). It is frequently selected for OCD when psychotic disorders or clozapine therapy coexist, provided its interaction profile is managed carefully.

The drug is a strong CYP1A2 and CYP2C19 inhibitor, so it can markedly elevate concentrations of clozapine, olanzapine, theophylline, caffeine, and warfarin—useful when deliberate but hazardous without monitoring.

Immediate-release tablets (25 mg, 50 mg, 100 mg) and extended-release capsules (100 mg, 150 mg) allow once-nightly or divided dosing. IR tablets are widely generic; ER capsules remain largely branded. Bedtime dosing and food can mitigate nausea and somnolence.

The compare view and fluvoxamine evidence feed can support balancing activation and interaction trade-offs when titrating complex regimens.

Mania/hypomania screening can be coordinated via the bipolar disorder hub, and the schizophrenia hub can support clozapine collaboration; counseling guides can be shared via the fluvoxamine print page.

In complex regimens, fluvoxamine is sometimes used to raise clozapine levels; this approach typically involves dose reductions, therapeutic drug monitoring (TDM) when available, and counseling about caffeine or smoking changes that can shift exposure.

Mechanism of Action

Refer to the Glossary entry on Neurotransmitters for background on receptor systems involved in serious mental illness.

Potent inhibition of the serotonin transporter with additional sigma-1 receptor agonism that may contribute to anxiolytic effects.

• High-affinity SERT inhibitor.
• Sigma-1 receptor agonist with minimal activity at histamine, adrenergic, or muscarinic receptors.

Metabolism and Pharmacokinetics

• Oral bioavailability ~53%; peak concentrations occur 3–8 hours post-dose for IR tablets.
• Elimination half-life averages 15–26 hours, lengthening in older adults or hepatic impairment.
• Extensive hepatic metabolism (CYP1A2 > CYP2D6/CYP2C19); fluvoxamine strongly inhibits CYP1A2/CYP2C19 and moderately inhibits CYP3A4/CYP2D6.
• Steady state is achieved in roughly 10 days; ~94% of metabolites are excreted renally with <1% unchanged drug.

Dosing and Administration

• Adults (IR): typical start is 50 mg at bedtime; increase by 50 mg every 4–7 days based on response. Usual range 100–300 mg/day (divide doses above 150 mg/day).
• Extended-release capsules: typical start is 100 mg nightly; titrate by 50 mg weekly to 300 mg/day for OCD (200 mg/day for SAD).
• Pediatrics (≥8 years, IR): typical start is 25 mg at bedtime; titration is no faster than weekly to a maximum of 200 mg/day with divided dosing over 50 mg.
• In hepatic impairment or geriatric patients, lower initial doses (often 25 mg daily) and slower titration are commonly used.
• Taper over at least 1–2 weeks to minimize discontinuation symptoms.

Adverse Effects

Interactions

• Contraindicated with MAOIs (including linezolid or IV methylene blue); appropriate washouts are required (commonly 14 days).
• Strong CYP1A2/CYP2C19 inhibition markedly raises levels of clozapine, olanzapine, theophylline, caffeine, tizanidine, and warfarin—dose reductions and monitoring of serum levels or clinical response are often needed.
• Moderate inhibition of CYP3A4/CYP2D6 can elevate benzodiazepines, beta-blockers, and TCAs; dose adjustment and monitoring may be needed.
• Combined serotonergic therapy (SSRIs/SNRIs, triptans, tramadol) increases serotonin syndrome risk—caution is common and symptom monitoring is important.
• Changes in smoking status alter CYP1A2 activity; interacting drug levels are reassessed when smoking status changes.

Other Useful Information

• Caffeine intake counseling is common; fluvoxamine can more than double caffeine exposure, worsening anxiety and insomnia.
• Coordination with prescribers managing clozapine or theophylline is common, including serum monitoring when fluvoxamine is initiated or discontinued.
• Weight, sleep quality, GI symptoms, and serum sodium are commonly monitored in higher-risk populations.

References

1. Fluvoxamine maleate tablets prescribing information — DailyMed (2025)
2. APA Clinical Practice Guideline FOR THE Treatment OF Patients With Obsessive Compulsive Disorder — American Psychiatric Association (2020)
3. Efficacy OF Fluvoxamine IN Obsessive Compulsive Disorder: A Double Blind Comparison With Placebo — Archives of General Psychiatry (1989)
4. CANMAT 2024 Clinical Guidelines for Major Depressive Disorder — Canadian Journal of Psychiatry (2024)
5. Consensus Guidelines for Therapeutic Drug Monitoring in Neuropsychopharmacology: Update 2017 — Pharmacopsychiatry (2018)
6. Fluvoxamine markedly increases clozapine levels — PubMed (1996)