Olanzipine
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Here is a comprehensive overview of Olanzapine based on authoritative pharmacology and psychiatry textbooks:
Olanzapine (Zyprexa)
Class & Chemistry
Olanzapine is a second-generation (atypical) antipsychotic (SGA) belonging to the thienobenzodiazepine structural class. Its receptor profile closely resembles clozapine, making it one of the broadest-acting antipsychotics available.
Mechanism of Action
Olanzapine is a high-affinity antagonist at multiple receptors:
| Receptor | Effect |
|---|---|
| 5-HT2A/2C, 5-HT6 | Serotonin blockade (8x stronger than D2 blockade) |
| D1-D4 (dopamine) | Antipsychotic action; D2 occupancy 68-84% at 10-20 mg doses |
| H1 (histamine) | Sedation, weight gain |
| α1-adrenergic | Orthostatic hypotension |
| M1-M5 (muscarinic) | Moderate - anticholinergic effects (dry mouth, constipation) |
| 5-HT3 | Moderate blockade |
Its 5-HT2A activity is approximately 8 times greater than its dopamine receptor blockade - this ratio is a defining feature of atypical antipsychotics and contributes to its lower EPS risk compared to first-generation agents.
- Kaplan & Sadock's Comprehensive Textbook of Psychiatry, p. 9261
Pharmacokinetics
| Parameter | Details |
|---|---|
| Absorption | Well absorbed orally; peak plasma at ~6 hours; food has minimal effect |
| Half-life | Mean ~31 hours (range 21-54 hrs); allows once-daily dosing |
| Steady state | Reached in ~7 days |
| IM route | Peak plasma in 15-45 minutes |
| Protein binding | 93% |
| Metabolism | Hepatic; direct glucuronidation + CYP1A2-mediated oxidation (major); also CYP2D6 and flavin mono-oxygenase |
| Active metabolites | None |
| Therapeutic drug monitoring | Recommended range: 20-80 ng/mL |
Drug interactions involving CYP1A2:
-
Inducers (omeprazole, rifampin, smoking, carbamazepine) decrease olanzapine levels
-
Inhibitors (fluvoxamine) increase olanzapine levels
-
Kaplan & Sadock's Comprehensive Textbook of Psychiatry, p. 9261
Indications & Clinical Use
1. Schizophrenia
- Effective against positive and negative symptoms; superior to haloperidol for negative symptoms and depression
- Superior to haloperidol in overall PANSS scores in first-episode schizophrenia
- IM formulation effective for acute agitation (similar efficacy to IM haloperidol)
- Dose range: typically 5-20 mg/day orally
2. Bipolar Disorder
- Approved for acute mania and mixed states (monotherapy or adjunct to lithium/valproate)
- Effective in both psychotic and non-psychotic mania
- Approved for bipolar maintenance (monotherapy)
- May be more effective than lithium for relapse prevention
- Effective even with carbamazepine, though one study showed olanzapine + carbamazepine was no better than carbamazepine alone
3. Bipolar I Depression / Treatment-Resistant MDD
- Olanzapine-fluoxetine combination (OFC) is FDA-approved for both conditions
4. Acute Agitation
- IM olanzapine is indicated for agitation in schizophrenia and bipolar I mania; advantage of rapid onset (~15-45 min to peak)
Adverse Effects
Metabolic (Most Clinically Significant)
| Adverse Effect | Details |
|---|---|
| Weight gain | Most prominent of all SGAs (except clozapine); CATIE study: ~2 lb/week; 56% gain >7% baseline weight; affects all BMI levels |
| Hyperlipidemia | Triglycerides most affected (mean +40.5 mg/dL in CATIE); total cholesterol and LDL also elevated; monitor lipids before and after starting |
| Hyperglycemia/T2DM | Increased risk of new-onset type 2 diabetes (OR ~5.8 vs non-antipsychotic users); can cause insulin resistance independent of weight gain; 73% of hyperglycemic cases appear within 6 months; potentially life-threatening (15 deaths reported in one survey) |
Monitoring required: Fasting glucose and lipids at baseline and regularly thereafter (APA and Mount Sinai Guidelines).
Other Adverse Effects
| Effect | Notes |
|---|---|
| Sedation | Due to H1 and muscarinic blockade |
| Orthostatic hypotension | α1 blockade |
| Elevated liver enzymes | ~2% with clinically significant ALT elevation (>3x ULN); no jaundice reported |
| Tardive dyskinesia / NMS | Same warnings as all antipsychotics (lower EPS risk than FGAs) |
| Prolactin elevation | Moderate; less than risperidone |
| Anticholinergic effects | Constipation, dry mouth, urinary retention |
Special Populations
Children & Adolescents
- Serious safety concerns: greater weight gain, liver enzyme elevations, prolactin elevation, elevated fasting glucose and cholesterol compared to adults
- The NIMH Data and Safety Monitoring Board closed randomization to olanzapine in one pediatric trial due to weight gain
- Should only be used when other antipsychotics have failed - Kaplan & Sadock's, p. 9262
Pregnancy
- Category C; associated with increased gestational diabetes risk (Medicaid data)
- No increased risk of malformations, but lower birth weight observed
Nursing Mothers
- Excreted in breast milk at ~1% of maternal dose; undetectable in infant plasma; all exposed infants in one study were healthy
Elderly (Dementia)
- Black box warning: Increased mortality in older patients with dementia-related psychosis compared to placebo
Formulations
| Form | Use |
|---|---|
| Oral tablet | Routine daily dosing |
| Orally disintegrating tablet (Zydis) | Patients who refuse or cannot swallow tablets |
| IM (short-acting) | Acute agitation |
| IM long-acting (Zyprexa Relprevv) | Maintenance in schizophrenia; carries risk of post-injection delirium/sedation syndrome |
| Olanzapine/samidorphan | Combination that minimizes metabolic effects; available in some countries |
Key Comparison Points
- Among SGAs, olanzapine has the greatest metabolic liability (except clozapine)
- It has the closest receptor profile to clozapine of any atypical antipsychotic
- Lower EPS risk than first-generation antipsychotics
- Therapeutic drug level monitoring (TDM) is recommended - target 20-80 ng/mL
- Smoking reduces olanzapine levels (CYP1A2 induction); advise monitoring after smoking cessation
Sources: Kaplan & Sadock's Comprehensive Textbook of Psychiatry; The Maudsley Prescribing Guidelines in Psychiatry, 15th ed.; Stahl's Essential Psychopharmacology
Recent evidence note: A 2024-2025 network meta-analysis (PMID 39128561) confirms olanzapine efficacy in pediatric acute mania but highlights its metabolic risks; a 2025 umbrella review (PMID 40133850) supports IM olanzapine for acute agitation management in psychiatric settings - consistent with the textbook evidence above.
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