What is the onset of action for 5 mg of Zyprexa (olanzapine) in an adult patient with a psychiatric condition?

Onset of Action for 5 mg Zyprexa (Olanzapine)

For oral olanzapine 5 mg, expect therapeutic effects to begin within 45-60 minutes, with peak effect at approximately 60 minutes, though full antipsychotic response for underlying psychiatric conditions requires several days to weeks of continued treatment. 1

Route-Specific Onset Times

Oral Administration (Standard or Orally Disintegrating Tablets)

• Oral olanzapine has an onset of action of 45-60 minutes with peak effects at 60 minutes, regardless of whether you use standard tablets or the Zydis orally disintegrating formulation 1
• Both oral formulations require the same time to reach therapeutic effect and are inappropriate for acute behavioral emergencies 2
• The orally disintegrating tablet (Zydis) dissolves rapidly in saliva but does not provide faster systemic absorption or clinical effect 3

Intramuscular Administration (For Comparison)

• IM olanzapine demonstrates significantly faster onset than oral formulations, with calming effects emerging within 15-30 minutes 4, 5
• IM olanzapine shows faster onset than IM haloperidol (which has sedation onset of approximately 28 minutes) 1

Important Clinical Context

Acute vs. Maintenance Effects

• The 45-60 minute onset refers to initial calming or sedative effects, not full antipsychotic efficacy 1
• For schizophrenia, therapeutic response evaluation should occur after 4-6 weeks of treatment at an adequate dose 6
• For bipolar disorder, short-term antimanic efficacy was demonstrated in 3-4 week clinical trials 3

Dosing Considerations for 5 mg

• The FDA label indicates that 5 mg is at the lower end of the therapeutic range (5-20 mg/day) for both schizophrenia and bipolar disorder 3
• When starting at 5 mg, dosage adjustments should occur at intervals of not less than 24 hours 3
• Lower doses like 5 mg may be appropriate for patients who are debilitated, predisposed to hypotensive reactions, or more pharmacodynamically sensitive to olanzapine 3

Common Pitfalls to Avoid

• Do not expect immediate tranquilization with oral olanzapine 5 mg—if rapid control of acute agitation is needed, IM formulation (10 mg) is the appropriate choice 2, 5
• Do not combine oral olanzapine with benzodiazepines without careful monitoring, as this combination increases risk of respiratory depression, particularly with high-dose olanzapine 1
• Do not assume the orally disintegrating tablet works faster—it only improves adherence in patients who might "cheek" medications, not speed of onset 2