olanzapine fluoxetine

Antipsychotic • Brands: Symbyax

Last reviewed: 2026-02-22

General information

Class: Antipsychotic
Common US brands: Symbyax
Typical dose range: Administer once daily in the evening. Label describes a common adult starting dose of 6 mg olanzapine / 25 mg fluoxetine (6/25) (label).
Therapeutic drug monitoring not routinely recommended.
Last reviewed: 2026-02-22

Dosing & forms

Forms/strengths: Oral capsules (mg olanzapine / mg fluoxetine): 3/25, 6/25, 6/50, 12/25, 12/50.
Frequency: Administer once daily in the evening. Label describes a common adult starting dose of 6 mg olanzapine / 25 mg fluoxetine (6/25) (label).
Typical range: Administer once daily in the evening. Label describes a common adult starting dose of 6 mg olanzapine / 25 mg fluoxetine (6/25) (label).

Mechanism (brief)

Fixed-dose combination of olanzapine (second-generation antipsychotic; D2/5-HT2A antagonism) and fluoxetine (SSRI). Indicated for bipolar I depression and treatment-resistant depression (label).

Metabolism & Half‑life

Metabolism: CYP1A2 (olanzapine), UGT1A4 (olanzapine), CYP2D6 (fluoxetine; and minor olanzapine pathway)
Half‑life: Single-dose mean 30 h

Therapeutic Drug Monitoring (TDM)

Recommended: No

View labelExact

Monitoring highlights

Metabolic monitoring (weight/BMI, lipids, glucose/A1c) is standard because olanzapine carries high risk for weight gain and metabolic effects (label/class).
Assess sedation, orthostasis, and functional safety (driving/work) during initiation and after dose changes (label/clinical).
Monitor mood and suicidality early in treatment, and screen for mania/hypomania activation in patients with bipolar risk (label/clinical).
Re-check interactions when medications or smoking status change: fluoxetine inhibits CYP2D6, and smoking can lower olanzapine exposure (label/clinical).

Sources

Olanzapine and fluoxetine capsules prescribing information — DailyMed (2025)
Efficacy of olanzapine and olanzapine-fluoxetine combination in the treatment of bipolar I depression — Archives of General Psychiatry (2003)
The CANMAT and ISBD Guidelines for the Management of Patients With Bipolar Disorder: 2021 Update — Bipolar Disorders (2021)
APA Clinical Practice Guideline for the Treatment of Depression — American Psychiatric Association (2023)
CANMAT 2024 Clinical Guidelines for Major Depressive Disorder — Canadian Journal of Psychiatry (2024)

Dosing & forms

Forms/strengths: Oral capsules (mg olanzapine / mg fluoxetine): 3/25, 6/25, 6/50, 12/25, 12/50.

Frequency: Administer once daily in the evening. Label describes a common adult starting dose of 6 mg olanzapine / 25 mg fluoxetine (6/25) (label).

Typical range: Administer once daily in the evening. Label describes a common adult starting dose of 6 mg olanzapine / 25 mg fluoxetine (6/25) (label).

Monitoring highlights

Metabolic monitoring (weight/BMI, lipids, glucose/A1c) is standard because olanzapine carries high risk for weight gain and metabolic effects (label/class).

Assess sedation, orthostasis, and functional safety (driving/work) during initiation and after dose changes (label/clinical).

Monitor mood and suicidality early in treatment, and screen for mania/hypomania activation in patients with bipolar risk (label/clinical).

Re-check interactions when medications or smoking status change: fluoxetine inhibits CYP2D6, and smoking can lower olanzapine exposure (label/clinical).