Guanabenz and Ma Huang: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Guanabenz
Ma Huang
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.
What happens
Increased blood pressure
Interaction Deep Dive
Pretreatment with clonidine augmented the pressor response to ephedrine1. Ma Huang (ephedra) is a natural source of ephedrine and pseudoephedrine 2. Ma Huang contains 0.5% to 2.5% of ephedra alkaloids. Ephedrine is the dominant alkaloid, comprising 30% to 90% of the total ephedra alkaloid content, depending on growing conditions 3. Use caution if Ma Huang and guanabenz are used concomitantly, as guanabenz is a central alpha-adrenergic agent like clonidine.
Why it happens (mechanism)
Increased catecholamine storage at sympathetic storage sites induced by guanabenz, enhanced sensitivity of tissue receptors, potentiation of alpha-adrenergic vasoconstriction, or a combination of these
Literature reports
1 report — tap to read
a) Pretreatment with oral clonidine 5 micrograms/kilogram resulted in a 10% to 27% increase in baseline mean blood pressure when ephedrine was administered, versus a 4% to 17% increase in patients receiving ephedrine alone. However, patients receiving clonidine had lower baseline blood pressures than those not receiving clonidine. More study is needed to confirm the clinical relevance of this interaction 1.
Common questions
Can I take Guanabenz and Ma Huang together?
Increased blood pressure Always confirm with your pharmacist or prescriber before making any change.
How serious is the Guanabenz and Ma Huang interaction?
It is rated moderate. Can be significant — usually manageable with monitoring.
How quickly could this interaction happen?
The documented onset is "rapid". Effects can appear quickly, often within about 24 hours of combining the drugs.
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 Guanabenz or Ma Huang 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 anything you'd monitor while I'm on both?
References (3)
- Nishikawa T, Kimura T, Taguchi N, et al: Oral clonidine preanesthetic medication augments the pressor responses to intravenous ephedrine in awake or anesthetized patients. Anesthesiology 1991; 74:705-710. PubMed
- White LM, Gardner SF, & Gurley BJ: Pharmacokinetics and cardiovascular effects of Ma-Huang (ephedra sinica) in normotensive adults. J Clin Pharmacol 1997; 37:116-122.
- Blumenthal M & King P: Ma huang: ancient herb, modern medicine, regulatory dilemma. Herbalgram 1995; 34:22-26, 43, 56-57.
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