Olanzapine (Zyprexa) Dosing Recommendations
Olanzapine should not be routinely administered twice daily (BID) as the standard dosing is once daily due to its long half-life of approximately 35 hours. 1
Standard Dosing Guidelines
- The recommended starting dose of olanzapine is 10 mg once daily, with a maximum recommended dose of 20 mg daily 2, 1
- Olanzapine reaches peak plasma levels in 5-8 hours and has a half-life of about 35 hours, making once-daily dosing appropriate for most patients 1
- The FDA-approved labeling indicates that Zyprexa (olanzapine) is usually taken one time each day 2
Special Considerations for Dose Adjustments
- If dose increases are needed, the total daily dose should be increased rather than splitting into multiple doses 3
- For elderly patients or those sensitive to side effects, lower starting doses (5 mg daily) with gradual titration is recommended 3, 4
- Dose adjustments should be made based on clinical response and tolerability, with at least 1-2 weeks between dose changes 3
Monitoring and Side Effects
- The most common side effects of olanzapine are somnolence and weight gain, with approximately 40% of patients experiencing weight gain 1
- Higher starting doses are associated with increased risk of weight gain, especially in underweight patients 1
- Monitor for orthostatic hypotension, particularly during initial dose titration 5
- Regular weight monitoring is essential as significant weight gain is common 2
Important Cautions
- Splitting the daily dose into BID dosing may increase the risk of side effects without providing additional therapeutic benefit 4
- If a dose is missed, take it as soon as remembered unless it's almost time for the next dose; do not take two doses at the same time 2
- Abrupt discontinuation should be avoided; tapering is recommended when stopping olanzapine 2
Alternative Approaches for Specific Situations
- For acute agitation or severe symptoms requiring rapid control, short-term BID dosing might be considered, but should be consolidated to once-daily dosing once stabilized 6
- For patients with bipolar disorder, once-daily dosing of 5-20 mg has demonstrated efficacy in clinical trials 6
Remember that olanzapine's pharmacokinetic profile supports once-daily dosing for most patients, and increasing to BID dosing should only be considered in specific clinical circumstances after evaluating the risk-benefit ratio.