Isocarboxazid and Clonidine Transdermal Patch: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Isocarboxazid
Clonidine 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
An increased risk of hypertension, headache, and related symptoms
Interaction Deep Dive
Concurrent use of isocarboxazid with sympathomimetics (or with over-the-counter drugs such as cold, hay fever, or weight reducing preparations that contain vasoconstrictors) is contraindicated as it may precipitate hypertension, headache, and related symptoms. During isocarboxazid therapy, it appears that some patients are particularly vulnerable to the effects of sympathomimetics when the activity of metabolizing enzymes is inhibited1.
Why it happens (mechanism)
Inhibition of metabolizing enzymes
Literature reports
3 reports — tap to read
a) The mechanism involved with this interaction is felt to be the release of catecholamine by the sympathomimetic drug. This results in liberation of a larger amount of norEPINEPHrine which is then available to combine with the receptor 2.
b) Sympathomimetics with indirect/mixed activity such as ePHEDrine cause the release of norEPINEPHrine, and the use of monoamine oxidase inhibitors (MAOIs) results in more norEPINEPHrine being made available at nerve receptor sites through inhibition of catecholamine degradation. Concurrent use leads to greater amounts of norEPINEPHrine, which increases sympathetic activity 3.
c) Coadministration of indirect-acting sympathomimetics and MAOIs has resulted in serious hypertension 4567.
Common questions
Can I take Isocarboxazid and Clonidine Transdermal Patch together?
An increased risk of hypertension, headache, and related symptoms Always confirm with your pharmacist or prescriber before making any change.
How serious is the Isocarboxazid and Clonidine Transdermal Patch interaction?
It is rated contraindicated. These should generally not be used together.
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 Isocarboxazid or Clonidine Transdermal Patch 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 (7)
- Product Information: MARPLAN oral tablets, isocarboxazid oral tablets. Validus Pharmaceuticals LLC (per Dailymed), Parsippany, NJ, 2023. DailyMed
- Goldberg LI: Monoamine oxidase inhibitors. Adverse reactions and possible mechanisms. JAMA 1964; 190:456-462. DOI
- Gilman AG, Rall TW, Nies AS, et alGilman AG, Rall TW, Nies AS, et al (Eds): Goodman and Gilman's The Pharmacological Basis of Therapeutics, 8th. Publishing Co, New York, NY, 1990.
- Smookler S & Bermudez AJ: Hypertensive crisis resulting from an MAO inhibitor and an over-the-counter appetite suppressant. Ann Emerg Med 1982; 11:482-484. PubMed
- Cuthbert MF, Greenberg MP, & Morley SW: Cough and cold remedies: a potential danger to patients on monoamine oxidase inhibitors. Br Med J 1969; 1:404-406. DOI
- Terry R, Kaye AH, & McDonald M: Sinutab (letter). Med J Aust 1975; 1:763.
- Horler AR & Wynne NA: Hypertensive crisis due to pargyline and metaraminol. Br Med J 1965; 2:460-461. PubMed
Keep reading about Isocarboxazid
Keep reading about Clonidine Transdermal Patch
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