Granisetron Transdermal Patch and Mirtazapine: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Mirtazapine
Granisetron Transdermal Patch
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.
What happens
Increased risk of serotonin syndrome, an increased risk of QT interval prolongation and an increased risk of torsades de pointes
Interaction Deep Dive
Use caution with concomitant use of mirtazapine with other drugs that prolong the QTc interval as it increases the risk of QT prolongation and/or ventricular arrhythmias. There have been postmarketing reports with mirtazapine and QT prolongation, torsades de pointes, ventricular tachycardia, and sudden death with the majority of cases occurring in association with overdose, known cardiovascular disease or family history of QT prolongation, or with the concomitant use of QTc-prolonging agent. Concomitant use of mirtazapine with other serotonergic agents may increase the risk of serotonin syndrome due to additive serotonergic effects. Monitor for symptoms of serotonin syndrome, especially during treatment initiation and dose increases, and if the patient shows symptoms, treatment with mirtazapine and discontinue any concomitant serotonergic agent23. Symptoms of serotonin syndrome include neuromuscular abnormalities, autonomic hyperactivity, and mental status changes. Serotonin syndrome can be life-threatening. If serotonin syndrome develops after discontinuation of the offending agents, provide supportive care and other therapy as necessary 1.
Why it happens (mechanism)
Additive serotonin effects; additive QT interval prolongation
Literature reports
3 reports — tap to read
a) Within a few hours of starting mirtazapine and shortly after stopping FLUoxetine, a 75-year-old woman experienced symptoms consistent with serotonin syndrome. Current medication for depression included FLUoxetine, chlorproMAZINE, and LORazepam. Due to lack of response, FLUoxetine was discontinued and soon afterward mirtazapine 30 mg/day was started. Within a few hours of starting mirtazapine, she experience dizziness, headache, nausea, dry mouth, intense anxiety and agitation with suicidal ideas. Other symptoms were difficulty walking, marked resting tremor of the hands, and insomnia. Over the next 3 days, she progressively worsened. Mirtazapine was discontinued on day 5. Her symptoms improved the following day. FLUoxetine 20 mg/day was restarted on day 7 with subsequent resolution of dizziness, nausea, headache, and agitation resolution over the following days. Over the next 10 days, tremor, anxiety, difficulty walking, dry mouth, and insomnia improved 4.
b) A 26-year-old woman with anorexia nervosa receiving fluvoxaMINE for 4 months developed symptoms of serotonin syndrome after mirtazapine was initiated. The symptoms of twitching, tremors, agitation, restlessness, and "feeling like she could crawl out of her skin" developed over a period of 4 days after starting mirtazapine 30 mg/day. Symptoms rapidly progressed to twitching, tremors, and restlessness. She was hospitalized with further symptoms of diaphoresis, flushing, fasciculations, and nausea and treated with cyproheptadine, acetaminophen, and IV fluids. She remained afebrile throughout the event. Symptoms completely resolved within 24 hours 5.
c) There have been postmarketing reports with mirtazapine and QT prolongation, torsades de pointes, ventricular tachycardia, and sudden death with the majority of cases occurring in association with overdose, known cardiovascular disease or family history of QT prolongation, or with the concomitant use of mirtazapine and QTc-prolonging agents 23.
Common questions
Can I take Granisetron Transdermal Patch and Mirtazapine together?
Increased risk of serotonin syndrome, an increased risk of QT interval prolongation and an increased risk of torsades de pointes Always confirm with your pharmacist or prescriber before making any change.
How serious is the Granisetron Transdermal Patch and Mirtazapine 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 strong is the evidence for this interaction?
The evidence is graded "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.
Questions for your pharmacist
- Does my dose of Granisetron Transdermal Patch or Mirtazapine 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 (5)
- Boyer EW & Shannon M: The serotonin syndrome. N Eng J Med 2005; 352(11):1112-1120. DOI
- Product Information: REMERON(R) oral tablets, mirtazapine oral tablets. Merck Sharp & Dohme Corp (per FDA), Whitehouse Station, NJ, 2020. DailyMed
- Product Information: Mirtazapine oral film coated tablets, mirtazapine oral film coated tablets. Apotex Corp (per DailyMed), Weston, FL, 2024. DailyMed
- Benazzi F: Serotonin syndrome with mirtazapine-fluoxetine combination. Int J Geriatr Psychiatry 1998; 13(7):495-496. DOI
- Demers JC & Malone M: Serotonin syndrome induced by fluvoxamine and mirtazapine. Ann Pharmacother 2001; 35:1217-1220. PubMed
Keep reading about Mirtazapine
Keep reading about Granisetron Transdermal Patch
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