Generic Name

Olanzapine

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Classification

FDA Approved Indications

• Schizophrenia
• Bipolar I disorder (manic or mixed episodes, bipolar maintenance)

Mechanism of Action

Olanzapine exerts its antipsychotic effects primarily through antagonism of dopamine D2 and serotonin 5-HT2A receptors, which helps modulate neurotransmission involved in psychosis and mood regulation.

Dosage and Administration

Adult: Start at 5-10 mg once daily; titrate based on response, up to a maximum of 20 mg/day.

Pediatric: Approved for adolescents ≥13 years; dosing varies based on condition, typically 5 mg/day initially, titrated as needed.

Geriatric: Use with caution; start at lower doses due to increased sensitivity and risk of adverse effects.

Renal Impairment: No specific adjustment needed, but monitor closely.

Hepatic Impairment: Start at lower dose; avoid rapid titration.

Pharmacokinetics

Absorption: Well absorbed orally; bioavailability approximately 60%.

Distribution: Widely distributed with a volume of distribution of approximately 100 L; 93% protein-bound.

Metabolism: Primarily hepatic via CYP1A2 and CYP2D6 pathways; undergoes extensive first-pass metabolism.

Excretion: Excreted mainly via urine (57%) and feces (30%).

Half Life: Approximately 21-54 hours, allowing once daily dosing.

Contraindications

• Hypersensitivity to olanzapine or other components.

Precautions

• Risk of metabolic syndrome (weight gain, hyperglycemia, dyslipidemia).
• Use cautiously in patients with cardiovascular disease, seizure disorders, or a history of neuroleptic malignant syndrome.
• Pregnancy Category C; potential risks vs benefits in pregnant women.
• Lactation: The drug passes into breast milk; weigh risks and benefits.

Adverse Reactions - Common

• Weight gain (Very common)
• Sedation (Common)
• Dizziness (Common)
• Dry mouth (Common)
• Dizziness (Common)

Adverse Reactions - Serious

• Extrapyramidal symptoms (Uncommon)
• Neuroleptic malignant syndrome (Rare)
• Hyperglycemia/diabetes mellitus (Uncommon)
• Orthostatic hypotension (Uncommon)
• QT prolongation (Uncommon)

Drug-Drug Interactions

• CNS depressants (enhanced sedation)
• drugs prolonging QT interval (increased risk of arrhythmias)
• CYP1A2 inducers (e.g., smoking) may decrease effectiveness
• CYP1A2 inhibitors (e.g., fluvoxamine) may increase levels

Drug-Food Interactions

• Caffeine may decrease olanzapine levels.

Drug-Herb Interactions

• St. John's Wort may decrease effectiveness.

Nursing Implications

Patient/Family Teaching

• Take medication exactly as prescribed; do not discontinue abruptly.
• Be aware of potential weight gain, increased blood sugar, and lipid levels.
• Report excessive drowsiness, movement problems, or signs of infection.
• Maintain regular follow-up appointments for monitoring.

Special Considerations

Black Box Warnings:

• Elderly patients with dementia-related psychosis treated with antipsychotics are at increased risk of death.

Genetic Factors: CYP1A2 genetic variations may influence drug levels.

Lab Test Interference: May increase serum prolactin levels

Overdose Management

Signs/Symptoms: Severe sedation, hypotension, extrapyramidal symptoms, coma.

Treatment: Supportive care, gastric lavage, activated charcoal if ingestion recent, and symptomatic management. No specific antidote.

Storage and Handling

Storage: Store at room temperature, 20-25°C (68-77°F), protected from light and moisture.

Stability: Stable for the duration of shelf life as per manufacturer instructions.