Olanzapine and Amitriptyline: Interaction Details
AI-assisted, pharmacist-reviewed · AI content regenerated Jul 11, 2026 · Source data updated Jul 2, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Amitriptyline
Olanzapine
No brand names on record
How we grade severity & evidence
Severity levels
- Contraindicated: These should generally not be used together.
- Major: Potentially serious — often needs a change or close monitoring.
- Moderate: Can be significant — usually manageable with monitoring.
- Minor: Usually limited clinical impact.
Evidence grades
- Established: Well documented — supported by controlled studies or strong clinical data.
- Probable: Good supporting evidence, though not definitively proven.
- Suspected: Some evidence suggests this interaction, but it is not well established.
- Possible: Limited or conflicting evidence; the interaction may occur.
- Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.
Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.
Amitriptyline (Elavil) and olanzapine can add up in two ways. Both can slow down your gut, and both can affect your heart's rhythm (something called QT prolongation). Together, you may have a higher risk of serious constipation or a very sluggish gut, and a small added risk of an irregular heartbeat.
The good news is this is a well-known combination that many care teams use safely. If you take both, watch for things like severe constipation, belly pain, feeling faint, or a racing or fluttering heartbeat, and let your doctor know. Please don't stop either medicine on your own, your pharmacist and doctor can monitor you and adjust things if needed.
Combination of amitriptyline (TCA) with olanzapine. Both agents carry anticholinergic activity and QT-prolonging potential.
- Direction/effect: Additive anticholinergic burden increases risk of severe GI hypomotility (constipation, ileus); additive QTc prolongation.
- Mechanism: Pharmacodynamic additivity. Note both share CYP1A2/CYP2D6 metabolism, so a PK component (mutually elevated levels) is plausible; neither is a prodrug.
- Evidence: Theoretical, supported by case-level data (seizures on TCA + olanzapine rechallenge).
- Management: Assess cumulative QT risk, baseline/periodic ECG and electrolytes (K+, Mg2+), monitor bowel function, avoid other QT-prolonging or anticholinergic agents. Doses individualized by the care team.
What happens
Increased risk of severe gastrointestinal adverse reactions and an increased risk of QT interval prolongation
Interaction Deep Dive
Exercise caution, because giving OLANZapine together with anticholinergic agents that prolong the QT interval may heighten the likelihood of serious gastrointestinal adverse effects and can produce additive prolongation of the QT interval1. Consider the case of a 34 year old man diagnosed with schizophrenia and OCD, who had no preexisting seizure disorder and sought treatment after prolonged noncompliance. He was started on inpatient OLANZapine therapy (20 mg/day), and his positive psychotic symptoms then resolved. He was discharged but returned to the hospital when his symptoms could not be managed. At that point clomiPRAMINE 250 mg/day was added. Within one week he experienced dizziness and myoclonic jerks that rapidly advanced to generalized motor seizures with postictal somnolence. His EEG showed spike waves and paroxysmal slowing, findings consistent with seizure activity. Both clomiPRAMINE and OLANZapine were then discontinued, and the seizures were brought under control with diazePAM 30 mg/day given over three days. The same sequence recurred when both OLANZapine and clomiPRAMINE were reintroduced. This adverse event can presumably be attributed to an interaction between the two medications. Both clomiPRAMINE and OLANZapine undergo metabolism via CYP1A2 and CYP2D6. One proposed explanation is that using them together could raise the concentrations of both agents. Even though the mechanism remains unclear, caution is recommended when OLANZapine is administered alongside clomiPRAMINE2.
Why it happens (mechanism)
Unknown; additive QT interval prolongation
How to manage this interaction
Care teams can manage this combination. Typically they will:
- Watch for severe constipation or a very slow gut, and for heart-rhythm changes (sometimes with an ECG).
- Keep an eye out for other medicines that also slow the gut or affect the QT interval.
- Individualize and adjust your doses if needed, and monitor you more closely, especially when starting or changing a dose.
What you can do: Keep taking both exactly as prescribed. Tell your pharmacist or prescriber about severe constipation, belly pain, dizziness, fainting, or a racing/irregular heartbeat, and check before adding any new medicine.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
2 reports — tap to read
a) A 34 year old man with schizophrenia and obsessive-compulsive disorder (OCD), with no preexisting seizure disorder, came for treatment after prolonged noncompliance. Inpatient therapy with OLANZapine (20 mg/day) was begun, and his positive psychotic symptoms then resolved. He was discharged and later readmitted because his symptoms could not be controlled. ClomiPRAMINE 250 mg per day was started. Within a week he reported dizziness and myoclonic jerks, which rapidly advanced to generalized motor seizures and postictal somnolence (without incontinence). The EEG showed spike waves and paroxysmal slowing consistent with seizure activity. ClomiPRAMINE and OLANZapine were then withheld, and the seizures were controlled with diazePAM 30 mg per day for three days. The same pattern recurred when the OLANZapine and clomiPRAMINE combination was reintroduced. Presumably from the temporal relationship between clomiPRAMINE and OLANZapine administration and the appearance of seizures, this adverse event may be suspected to arise from an interaction between the two drugs. Both clomiPRAMINE and OLANZapine are metabolized by CYP1A2 and CYP2D6. One theory is that giving them together may lead to increased levels of both agents. Although the mechanism behind this interaction is not yet known, caution is advised when OLANZapine is given together with clomiPRAMINE, or with other agents known to lower the seizure threshold 2.
b) In postmarketing experience, the risk of severe adverse reactions (including deaths) was heightened when anticholinergic medications were used concurrently 1.
Common questions
Can I take Olanzapine and Amitriptyline together?
Taking amitriptyline with olanzapine can add up to worsen constipation/gut slowing and slightly raise heart-rhythm (QT) risk, so keep taking both as prescribed and report severe constipation, fainting, or an irregular heartbeat to your care team. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Olanzapine and Amitriptyline interaction?
It is rated major. Potentially serious — often needs a change or close monitoring.
How quickly could this interaction happen?
The documented onset is "unspecified". The timing of this interaction is not well characterized.
How is the Olanzapine and Amitriptyline interaction managed?
Care teams can manage this combination. Typically they will: Watch for severe constipation or a very slow gut, and for heart-rhythm changes (sometimes with an ECG). Keep an eye out for other medicines that also slow the gut or affect the QT interval. Individualize and adjust your doses if needed, and monitor you more closely, especially when starting or changing a dose. What you can do: Keep takin… Management is individual — always follow your own care team's guidance.
How strong is the evidence for this interaction?
The evidence is graded "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.
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Questions for your pharmacist
- Does my dose of Olanzapine or Amitriptyline need adjusting while I take them together?
- What symptoms should prompt me to call you or my prescriber right away?
- Does the timing of my doses matter for this combination?
- Is there a safer alternative to one of these medications for me?
References (2)
- Product Information: LYBALVI(R) oral tablets, olanzapine samidorphan oral tablets. Alkermes Inc (per FDA), Waltham, MA, 2024. DailyMed
- Deshauer D, Albuquerque J, Alda M, et al: Seizures caused by possible interaction between olanzapine and clomipramine. J Clin Psychopharmacol 2000; 20 (2):283-284. PubMed
Keep reading about Amitriptyline
Keep reading about Olanzapine
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