What is the recommended starting dose of olanzapine (atypical antipsychotic)?

Recommended Starting Dose of Olanzapine

The recommended starting dose of olanzapine is 2.5-5 mg orally once daily, with dose adjustments based on clinical response and patient factors. 1, 2

General Dosing Guidelines

• Initial dosing should be 2.5-5 mg orally once daily (usually at bedtime) for most patients 1
• For scheduled dosing beyond initial treatment, start with 2.5-5 mg daily 1
• Olanzapine is available as oral tablets and orally disintegrating tablets (ODT) 1
• The medication can be administered without regard to meals 2
• Dose adjustments, when needed, should generally occur at intervals of not less than 1 week, as steady state is not achieved for approximately 1 week 2

Patient-Specific Dosing Considerations

Reduced Starting Doses (2.5 mg)

• Elderly patients 1, 2
• Patients with hepatic impairment 1
• Debilitated patients 2
• Patients predisposed to hypotensive reactions 2
• Non-smoking female patients ≥65 years of age 2
• Patients who may metabolize olanzapine more slowly 2

Administration Routes

• Primary route is oral (p.o.) 1
• Can also be given subcutaneously (s.c.) or intramuscularly (i.m.) in certain clinical situations 1

Important Monitoring and Safety Considerations

• Monitor for common side effects including:

  • Drowsiness and sedation 1, 3
  • Orthostatic hypotension 1
  • Weight gain (occurs in approximately 40% of patients) 3, 4
  • Metabolic effects with long-term use 1

• Use caution when combining with benzodiazepines due to risk of oversedation and respiratory depression 1

• Fatalities have been reported with concurrent use of benzodiazepines and high-dose olanzapine 1

• QTc prolongation is less common with olanzapine compared to some other antipsychotics 3, 4

Special Populations

• For schizophrenia in adolescents, the FDA-approved starting dose is 2.5-5 mg daily 2
• For bipolar disorder, starting doses are typically higher (10-15 mg daily) in adults 2
• In patients with Alzheimer's disease, a lower starting dose of 2.5 mg is recommended 1

Clinical Pearls

• Olanzapine reaches peak plasma levels in 5-8 hours and has a half-life of approximately 35 hours 3
• Smoking status significantly affects olanzapine plasma levels, with smokers typically requiring higher doses 5
• Fluvoxamine co-administration can significantly increase olanzapine plasma levels 5
• Lithium and some other medications may lower olanzapine plasma concentrations 5
• The maximum recommended dose is generally 20 mg daily, though higher doses have been used in clinical practice 2, 3