Olanzapine IV to PO Conversion
Olanzapine has a one-to-one conversion ratio between intravenous (IV) and oral (PO) administration. This is evident from the National Comprehensive Cancer Network (NCCN) guidelines which consistently list the same 10 mg dose for olanzapine regardless of whether it's administered orally or intravenously in antiemetic regimens 1.
Evidence Supporting 1:1 Conversion
The NCCN Antiemesis Guidelines (2017) clearly demonstrate the equivalent dosing between IV and PO olanzapine:
- In antiemetic regimens for highly emetogenic chemotherapy, olanzapine is dosed at 10 mg whether given orally or intravenously 1
- When olanzapine is used in combination with palonosetron and dexamethasone, the olanzapine dose remains consistent at 10 mg regardless of route of administration 1
Clinical Applications
Antiemetic Use
- For chemotherapy-induced nausea and vomiting, olanzapine is administered at 10 mg PO once daily for 3-4 days 1
- When transitioning from IV to PO in this setting, the same 10 mg dose is maintained 1
Psychiatric Use
- In the management of acute agitation in schizophrenia, studies have shown successful transition from IM olanzapine 10 mg to oral olanzapine 5-20 mg/day without dosage adjustment 2
- A retrospective study examining IV olanzapine administration in emergency departments used the same dosing ranges for IV as typically used for oral administration (2.5 mg, 5 mg) 3
Safety Considerations
When administering olanzapine intravenously:
- Hypotension may occur in approximately 5.2% of administrations 4
- Bradycardia has been reported in about 1.3% of IV administrations 4
- Phlebitis is rare (1.4% of administrations) 4
- Respiratory depression should be monitored, particularly when combined with other sedative medications 3
Important Caveats
While the evidence supports a 1:1 conversion ratio, individual patient factors should be considered:
The optimal therapeutic range for olanzapine serum levels is 20-40 ng/mL, with concentrations above 80 ng/mL associated with increased adverse events 5
Unlike some other medications that require dosage adjustments when changing routes (such as certain opioids that use a 2:1 or 3:1 oral-to-parenteral ratio), olanzapine maintains its potency across different routes of administration 6
Bottom Line
When transitioning patients between IV and PO olanzapine, maintain the same dose. The pharmacokinetic properties of olanzapine allow for this straightforward 1:1 conversion, making it simpler to manage compared to medications requiring complex conversion calculations.