OLANZAPINE AND FLUOXETINE HYDROCHLORIDE
Clinical safety rating: safe
Animal studies have demonstrated safety
Olanzapine is an atypical antipsychotic that antagonizes dopamine D2 and serotonin 5-HT2A receptors. Fluoxetine is a selective serotonin reuptake inhibitor (SSRI). The combination modulates serotonergic and dopaminergic pathways to treat depressive episodes in bipolar I disorder.
| Metabolism | Olanzapine: primarily metabolized by CYP1A2 and glucuronidation. Fluoxetine: extensively metabolized by CYP2D6 and CYP2C9 to active metabolite norfluoxetine. |
| Excretion | Olanzapine: ~57% renal (metabolites), ~30% fecal. Fluoxetine: ~80% renal (metabolites, mainly norfluoxetine), ~15% fecal. |
| Half-life | Olanzapine: 30 h (young adults); 50 h (elderly). Fluoxetine: 4-6 days (single dose), 4-6 days (norfluoxetine); longer with chronic dosing (up to 6-8 weeks to steady state). Clinical context: drug accumulates over weeks. |
| Protein binding | Olanzapine: 93% bound to albumin and α1-acid glycoprotein. Fluoxetine: 94-95% bound to albumin and α1-acid glycoprotein. |
| Volume of Distribution | Olanzapine: ~15 L/kg (extensive tissue distribution). Fluoxetine: 35 L/kg (extensive distribution, including brain). |
| Bioavailability | Olanzapine: ~60% oral (60% absorbed, extensive first-pass). Fluoxetine: >90% oral (well absorbed, minimal first-pass). |
| Onset of Action | Oral: 2-4 weeks for antidepressant/antipsychotic effect. Initial improvement may be seen within 1-2 weeks. |
| Duration of Action | Plasma levels sustained for days due to long half-life; clinical effect persists for weeks after discontinuation. Therapeutic levels maintained with once-daily dosing. |
Olanzapine 6 mg / fluoxetine 25 mg orally once daily in the evening, with dose adjustments based on response and tolerability.
| Dosage form | CAPSULE |
| Renal impairment | No dosage adjustment required for mild to moderate renal impairment (CrCl ≥30 mL/min). For severe renal impairment (CrCl <30 mL/min), use with caution but no specific guidelines available. |
| Liver impairment | For Child-Pugh Class A or B: start olanzapine 5 mg / fluoxetine 20 mg once daily; for Child-Pugh Class C: avoid use due to lack of data and potential for reduced clearance. |
| Pediatric use | For children 10-17 years: initial dose olanzapine 2.5 mg / fluoxetine 10 mg orally once daily; titrate to usual range of olanzapine 6 mg / fluoxetine 25 mg once daily; maximum dose olanzapine 12 mg / fluoxetine 50 mg once daily. |
| Geriatric use | Initiate at olanzapine 3 mg / fluoxetine 20 mg orally once daily; increase slowly with close monitoring for orthostatic hypotension, extrapyramidal symptoms, and metabolic effects. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
CNS depressants may enhance sedative effects Can cause metabolic changes including weight gain hyperlipidemia and hyperglycemia.
| Breastfeeding | Both olanzapine and fluoxetine are excreted into breast milk. The milk-to-plasma (M/P) ratio for olanzapine is approximately 0.3; for fluoxetine and its active metabolite norfluoxetine, the M/P ratio is about 0.7 and 0.5, respectively. Relative infant doses are estimated at 1-3% for olanzapine and 2-12% for fluoxetine/norfluoxetine. Infants should be monitored for sedation, poor feeding, irritability, and weight gain. Breastfeeding is generally considered acceptable with caution, especially in preterm or ill infants. |
| Teratogenic Risk | First trimester: Limited data; fluoxetine is a known SSRI associated with a small increased risk of cardiovascular malformations (primarily septal defects) with first-trimester exposure. Olanzapine has not shown a clear increase in major malformations, but data are limited. Second and third trimesters: SSRI exposure (fluoxetine) may increase risk of persistent pulmonary hypertension of the newborn (PPHN) and poor neonatal adaptation syndrome (PNAS), including respiratory distress, feeding difficulties, irritability, and tremors. Third-trimester exposure to olanzapine may cause extrapyramidal symptoms and withdrawal in neonates. |
■ FDA Black Box Warning
Increased risk of suicidal thinking and behavior in children, adolescents, and young adults taking antidepressants. Olanzapine/fluoxetine is not approved for use in patients under 10 years of age.
| Common Effects | Dizziness Sleepiness Orthostatic hypotension sudden lowering of blood pressure on standing Dryness in mouth Weight gain Increased prolactin level in blood Constipation Muscle stiffness Restlessness Tremors |
| Serious Effects |
["Concomitant use with MAOIs (monoamine oxidase inhibitors) or within 14 days of discontinuing MAOI","Concomitant use with thioridazine or pimozide","Known hypersensitivity to olanzapine or fluoxetine"]
| Precautions | ["Suicidality: Monitor for worsening depression and suicidal thoughts, especially early in treatment","Metabolic changes: Hyperglycemia, dyslipidemia, weight gain","Extrapyramidal symptoms and tardive dyskinesia","Neuroleptic malignant syndrome (NMS)","Serotonin syndrome","Hyperprolactinemia","Orthostatic hypotension","QT interval prolongation","Leukopenia/neutropenia","Seizures","Impaired cognitive and motor function"] |
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| Fetal Monitoring | Maternal: Monitor weight, blood glucose, lipids, and blood pressure due to metabolic risks of olanzapine; monitor for serotonin syndrome or neuroleptic malignant syndrome. Fetal/neonatal: Ultrasound for fetal growth and anatomy; neonatal monitoring for PNAS, extrapyramidal symptoms, and respiratory adaptation for at least 48 hours after delivery. |
| Fertility Effects | Olanzapine can cause hyperprolactinemia, potentially leading to menstrual irregularities, galactorrhea, and reduced fertility. Fluoxetine may cause sexual dysfunction but has not been consistently linked to impaired fertility. In men, olanzapine may reduce sperm quality. Overall, use may decrease fertility due to hormonal effects. |