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SSRI (Selective Serotonin Reuptake Inhibitor) — OCD Specialist Pregnancy: Avoid in first trimester and near delivery — neonatal abstinence syndrome and persistent pulmonary hypertension risk. Sertraline preferred if antidepressant needed in pregnancy.

Fluvoxamine

Brand names: Faverin

Adult dose

Dose: OCD: 50mg OD at night initially; increase by 50mg every 4–7 days; usual range 100–300mg daily. Doses above 150mg in divided doses (BD–TDS). Depression (licensed but not commonly used): 50–100mg OD initially; increase to 100–300mg daily.
Route: Oral
Frequency: Once daily at night (low doses) or divided doses (>150mg)
Max: 300mg daily
Potent CYP1A2 and CYP3A4 inhibitor — significant drug interaction burden (the most interaction-heavy SSRI). Particularly effective for OCD. Less sedating than clomipramine but comparable efficacy for OCD in most meta-analyses. Avoid grapefruit. Strong sigma-1 receptor activity (potential anti-inflammatory effect — investigated in COVID-19).

Paediatric dose

Route: Oral
Frequency: Once daily or twice daily
Max: 200mg daily
BNFc: OCD (8–17 years): 25mg OD at night initially; increase by 25mg every 4–7 days to 50–200mg daily (doses >50mg in 2 divided doses). Seek specialist child and adolescent psychiatry opinion.

Dose adjustments

Renal

Use with caution in severe renal impairment — start at lower dose.

Hepatic

Reduce dose in hepatic impairment — hepatically metabolised; start at 50mg OD and titrate slowly.

Clinical pearls

  • Most interaction-heavy SSRI — conduct detailed medication review before prescribing; interactions with clozapine, theophylline, agomelatine, and tizanidine are particularly important and potentially dangerous
  • Clozapine interaction: fluvoxamine significantly increases clozapine plasma levels (CYP1A2 inhibition) — if co-prescribed, clozapine dose must be reduced by 50–75% and levels monitored closely (this combination is sometimes used intentionally in clozapine-resistant schizophrenia)
  • OCD evidence: one of the best-evidenced SSRIs for OCD alongside sertraline and fluoxetine; licensed and recommended by NICE CG31
  • Sigma-1 agonism: fluvoxamine investigated as COVID-19 treatment due to sigma-1 receptor anti-inflammatory effects (TOGETHER trial) — emerging data, not current standard of care

Contraindications

  • MAOIs (within 14 days — serotonin syndrome)
  • Tizanidine — contraindicated (CYP1A2 inhibition causes 10-fold increase in tizanidine levels — severe hypotension and sedation)
  • Thioridazine, pimozide — QTc risk
  • Hypersensitivity to fluvoxamine

Side effects

  • Nausea (very common, particularly at initiation)
  • Somnolence
  • Dry mouth
  • Constipation
  • Agitation
  • Sexual dysfunction
  • Hyponatraemia (SIADH)
  • Serotonin syndrome (with interacting drugs)

Interactions

  • CYP1A2 inhibitor (potent): increases theophylline, clozapine, duloxetine, agomelatine, caffeine levels significantly — avoid or reduce doses of these drugs
  • CYP3A4 inhibitor: increases benzodiazepine (alprazolam, triazolam), buspirone, carbamazepine levels
  • Tizanidine — contraindicated (see above)
  • Warfarin — increases warfarin levels; monitor INR closely
  • MAOIs — contraindicated

Monitoring

  • OCD symptom rating (Y-BOCS)
  • Drug interaction review (critical at initiation)
  • Sodium in elderly (hyponatraemia)
  • Mood and suicidality (first 4 weeks)

Reference: BNFc; BNF 90; NICE CG31 (OCD); NICE CG90 (Depression). Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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