What is the recommended dosage and treatment protocol for Fluvoxamine (Selective Serotonin Reuptake Inhibitor) in treating obsessive-compulsive disorder (OCD) and other anxiety disorders?

Fluvoxamine Dosing and Treatment Protocol for OCD and Anxiety Disorders

Recommended Dosing for Adults with OCD

For adult patients with OCD, start fluvoxamine at 50 mg once daily at bedtime, then increase by 50 mg increments every 4-7 days as tolerated to a target range of 100-300 mg/day, with doses above 100 mg split into two divided doses (larger dose at bedtime). 1

Specific Dosing Algorithm:

• Initial dose: 50 mg at bedtime 1
• Titration schedule: Increase by 50 mg every 4-7 days based on tolerability 1
• Therapeutic range: 100-300 mg/day (established in controlled trials) 2, 1
• Maximum dose: 300 mg/day 1
• Dosing frequency: Single daily dose up to 100 mg; split into two divided doses (unequal, with larger dose at bedtime) when exceeding 100 mg 1

Treatment Duration:

• Acute treatment: Minimum 8-10 weeks at maximum tolerated dose to assess response 3
• Maintenance therapy: 12-24 months for responders to prevent relapse 3
• Long-term efficacy: While controlled trials only documented efficacy beyond 10 weeks, OCD is chronic and continuation is reasonable for responding patients 1

Pediatric Dosing (Ages 8-17)

For children and adolescents with OCD, start at 25 mg at bedtime, increase by 25 mg every 4-7 days, with maximum doses of 200 mg/day for children up to age 11 and 300 mg/day for adolescents. 1

Age-Specific Considerations:

• Children (ages 6-11): Maximum 200 mg/day due to 2-3 times higher steady-state plasma concentrations compared to adolescents 4, 5
• Adolescents (ages 12-17): Maximum 300 mg/day (similar pharmacokinetics to adults) 4, 5
• Gender consideration: Therapeutic effect in female children may be achieved with lower doses 1
• Dosing frequency: Split doses above 50 mg, with larger dose at bedtime 1

Treatment Protocol for Anxiety Disorders

Fluvoxamine is effective for social anxiety disorder, panic disorder, and generalized anxiety disorder at doses of 100-300 mg/day for 6-8 weeks. 3, 6

First-Line Treatment Selection:

The choice between fluvoxamine and CBT depends on specific clinical factors 3:

Choose fluvoxamine when:

• Patient prefers medication over CBT 3
• Severe OCD prevents engagement with CBT 3
• Comorbid major depression or other conditions where SSRIs are indicated 3
• CBT is unavailable 3

Choose CBT when:

• Patient prefers psychotherapy 3
• No comorbid disorders requiring medication 3
• SSRIs contraindicated (bipolar disorder, pregnancy, intolerance) 3

Response Assessment and Next Steps:

Good response (after 8-10 weeks at therapeutic dose):

• Continue maintenance therapy for 12-24 months 3
• Add CBT if available for enhanced benefit 3
• Consider monthly booster sessions for 3-6 months 3

Inadequate response:

• Combine with CBT if not already doing so 3
• If CBT unavailable, switch to second SSRI or clomipramine 3
• Consider augmentation with atypical antipsychotics or glutamate-modulating agents 3

Special Populations

Elderly and Hepatically Impaired:

Use lower initial doses and slower titration due to decreased clearance of fluvoxamine in these populations. 1

Pregnancy (Third Trimester):

Carefully weigh risks versus benefits; consider tapering in third trimester due to neonatal complications (prolonged hospitalization, respiratory support, tube feeding requirements). 1

Critical Drug Interactions and Safety Concerns

Contraindications:

• Absolute contraindication: Concomitant use with MAOIs due to serotonin syndrome risk 3
• Avoid: Alprazolam and triazolam due to significant interaction risk 2

Cytochrome P450 Interactions:

Fluvoxamine is a potent CYP1A2 inhibitor and moderate inhibitor of CYP2C19, CYP3A4, and CYP2D6, requiring careful monitoring of interacting medications. 3, 2, 6

This represents a more significant interaction profile compared to other SSRIs like citalopram/escitalopram, which have minimal CYP450 effects 3.

Serotonin Syndrome Risk:

Monitor when combining with other serotonergic agents including 3:

• Other antidepressants (SSRIs, SNRIs, TCAs)
• Opioids (tramadol, meperidine, methadone, fentanyl)
• Dextromethorphan
• Stimulants
• St. John's wort, L-tryptophan

Symptoms appear within 24-48 hours: confusion, agitation, tremors, hyperreflexia, autonomic instability (hypertension, tachycardia, diaphoresis) 3

Discontinuation Protocol

Taper gradually rather than stopping abruptly to minimize discontinuation syndrome, which is more common with fluvoxamine due to its shorter half-life. 3, 2, 1

Discontinuation Syndrome Symptoms:

• Dizziness, fatigue, myalgias, headaches 3
• Nausea, vomiting, diarrhea 3
• Sensory disturbances, paresthesias 3
• Anxiety, irritability, agitation 3

Management: If intolerable symptoms occur, resume previous dose and taper more slowly 1

Common Adverse Effects

Nausea is the most common adverse effect (>10% of patients), with other events including somnolence, asthenia, headache, dry mouth, and insomnia occurring less frequently. 6

• Lower risk of anticholinergic and cardiovascular effects compared to tricyclic antidepressants 6
• Low risk of suicidal behavior and sexual dysfunction 6
• Generally well tolerated with similar adverse event profile to other SSRIs 6
• In pediatric patients, abdominal discomfort occurs more frequently than with placebo 4, 5

Controlled-Release Formulation

A controlled-release formulation offers once-daily dosing with less daily fluctuation in drug levels and potentially more rapid onset of effect, without increased adverse events compared to immediate-release formulation 7.