Olanzapine with Haloperidol Interaction Details
Brand Names Associated with Olanzapine
- Olanzapine
- Symbyax® (as a combination product containing Fluoxetine, Olanzapine )
- Zyprexa®
- Zyprexa® Zydis
Brand Names Associated with Haloperidol
- Haldol®
- Haloperidol
Medical Content Editor Dr. Brian Staiger, PharmD
Last updated
Dec 03, 2023
Interaction Effect
Increased risk of QT interval prolongation, an increased risk of CNS depression and an increased risk of parkinsonism (cogwheeling rigidity, unstable gait)
Interaction Summary
Coadministration of OLANZapine with other QT prolonging drugs like haloperidol may increase the risk of QT interval prolongation. Additionally, use caution if the concomitant administration of OLANZapine and other CNS-active drugs like haloperidol is required. In evaluating individual cases, consider using lower initial doses of the concomitantly administered drugs, using conservative titration schedules, and monitoring clinical status. A patient receiving haloperidol experienced extreme parkinsonism following the addition of OLANZapine therapy. Possible explanations include a pharmacokinetic interaction between OLANZapine, a weak cytochrome P450 2D6 (CYP2D6) inhibitor, and haloperidol, a CYP2D6 substrate. Pharmacodynamically, the small amount of dopamine (D2) blockade from OLANZapine may have been enough to increase the patient's parkinsonism .
Severity
Major
Onset
Delayed
Evidence
Probable
How To Manage Interaction
Coadministration of OLANZapine with other QT prolonging drugs like haloperidol may increase the risk of QT interval prolongation. Additionally, use caution if the concomitant administration of OLANZapine and other CNS-active drugs like haloperidol is required. In evaluating individual cases, consider using lower initial doses of the concomitantly administered drugs, using conservative titration schedules, and monitoring clinical status.
Mechanism Of Interaction
Additive QT interval prolongation; additive CNS depression; inhibition of CYP2D6-mediated haloperidol metabolism; increased dopamine D2 blockade
Literature Reports
A) A 67-year-old hospitalized male with bipolar disorder who had stopped taking his medications was restarted on haloperidol 10 mg nightly, benztropine 1 mg nightly, and valproate 750 mg twice daily. He had been experiencing some mild parkinsonian symptoms at baseline, but these symptoms did not worsen when haloperidol was reinstituted. Following stabilization on this regimen, it was decided to change his antipsychotic medication to OLANZapine to minimize any parkinsonism that was a result of his medications. While tapering the haloperidol and initiating OLANZapine, the patient experienced extreme parkinsonism that resulted in an inability to walk. His mental status remained unchanged. Haloperidol was discontinued on day 7 of combination therapy, and two days later the patient's parkinsonism side effects had resolved back to baseline. Benztropine was then discontinued, and the parkinsonian symptoms did not reoccur while on OLANZapine .
Olanzapine Overview
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Olanzapine is used to treat the symptoms of schizophrenia (a mental illness that causes disturbed or unusual thinking, loss of interest in life, and strong or inappropriate emotions) in adults and teenagers 13 years of age and older. It is also used to treat bipolar disorder (manic depressive disorder; a disease that causes episodes of depression, episodes of mania, and other abnormal moods) in adults and teenagers 13 years of age and older. Olanzapine is in a class of medications called atypical antipsychotics. It works by changing the activity of certain natural substances in the brain.
Haloperidol Overview
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Haloperidol is used to treat psychotic disorders (conditions that cause difficulty telling the difference between things or ideas that are real and things or ideas that are not real). Haloperidol is also used to control motor tics (uncontrollable need to repeat certain body movements) and verbal tics (uncontrollable need to repeat sounds or words) in adults and children who have Tourette's disorder (condition characterized by motor or verbal tics). Haloperidol is also used to treat severe behavioral problems such as explosive, aggressive behavior or hyperactivity in children who cannot be treated with psychotherapy or with other medications. Haloperidol is in a group of medications called conventional antipsychotics. It works by decreasing abnormal excitement in the brain.
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Definitions
Severity Categories
Contraindicated
These drugs, generally, should not be used together simultaneously due to the high risk of severe adverse effects. Combining these medications can lead to dangerous health outcomes and should be strictly avoided unless otherwise instructed by your provider.
Major
This interaction could result in very serious and potentially life-threatening consequences. If you are taking this drug combination, it is very important to be under close medical supervision to minimize severe side effects and ensure your safety. It may be necessary to change a medication or dosage to prevent harm.
Moderate
This interaction has the potential to worsen your medical condition or alter the effectiveness of your treatment. It's important that you are monitored closely and you potentially may need to make adjustments in your treatment plan or drug dosage to maintain optimal health.
Minor
While this interaction is unlikely to cause significant problems, it could intensify side effects or reduce the effectiveness of one or both medications. Monitoring for changes in symptoms and your condition is recommended, and adjustments may be made if needed to manage any increased or more pronounced side effects.
Onset
Rapid: Onset of drug interaction typically occurs within 24 hours of co-administration.
Delayed: Onset of drug interaction typically occurs more than 24 hours after co-administration.
Evidence
Level of documentation of the interaction.
Established: The interaction is documented and substantiated in peer-reviewed medical literature.
Theoretical: This interaction is not fully supported by current medical evidence or well-documented sources, but it is based on known drug mechanisms, drug effects, and other relevant information.
How To Manage The Interaction
Provides a detailed discussion on how patients and clinicians can approach the identified drug interaction as well as offers guidance on what to expect and strategies to potentially mitigate the effects of the interaction. This may include recommendations on adjusting medication dosages, altering the timing of drug administration, or closely monitoring for specific symptoms.
It's important to note that all medical situations are unique, and management approaches should be tailored to individual circumstances. Patients should always consult their healthcare provider for personalized advice and guidance on managing drug interactions effectively.
Mechanism Of Interaction
The theorized or clinically determined reason (i.e., mechanism) why the drug-drug interaction occurs.
Disclaimer: The information provided on this page is for informational purposes only and should not be considered medical advice. Always consult with a qualified healthcare professional regarding your specific circumstances and medical conditions.
Where Does Our Information Come From?
Information for our drug interactions is compiled from several drug compendia, including:
The prescribing information for each drug, as published on DailyMED, is also used.
Individual drug-drug interaction detail pages contain references specific to that interaction. You can click on the reference number within brackets '[]' to see what reference was utilized.
The information posted is fact-checked by HelloPharmacist clinicians and reviewed quarterly.