Drug & supplement interaction

Reishi Mushroom + Phenoxybenzamine

Phenoxybenzamine brand name: Dibenzyline.

Moderate Interaction
Medically reviewed by · Updated September 2026
The bottom line Moderate

Reishi Mushroom has a moderate interaction with Phenoxybenzamine. Theoretically, concurrent use of reishi mushroom with antihypertensive drugs might increase the risk of hypotension.

Read the full interaction report
SeverityModerate
LikelihoodPossible
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Reishi Mushroom and Phenoxybenzamine

Here is the interaction we found between these two, with the evidence behind it.

Moderate

ANTIHYPERTENSIVE DRUGS

Why this applies to Phenoxybenzamine

Phenoxybenzamine falls under ANTIHYPERTENSIVE DRUGS — the group Reishi Mushroom interacts with.

Theoretically, concurrent use of reishi mushroom with antihypertensive drugs might increase the risk of hypotension.
Reishi mushroom has shown hypotensive activity in animal research. Clinical evidence suggests that reishi mushroom reduces blood pressure in some, but not all, patients with hypertension.
Severity Moderate Likelihood Possible Evidence D

Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the gist: phenoxybenzamine already lowers blood pressure by blocking alpha receptors, which is why it can leave you feeling lightheaded or dizzy, especially when you stand up quickly. Reishi mushroom has shown its own mild blood-pressure-lowering activity in animal and some human studies, so stacking the two together could, in theory, add up and push your pressure down a little more than expected.

I want to be honest about the evidence here. This is mostly lab and animal data, with mixed results in people, so it's a possible concern rather than a proven one. Still, since phenoxybenzamine can cause fainting and a racing heartbeat, it's worth a quick chat with your pharmacist or doctor before adding reishi.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Lee SY, Rhee HM. Cardiovascular effects of mycelium extract of Ganoderma lucidum: inhibition of sympathetic outflow as a mechanism of its hypotensive action. Chem Pharm Bull (Tokyo) 1990;38:1359-64. PubMed
  2. Kabir, Y., Kimura, S., and Tamura, T. Dietary effect of Ganoderma lucidum mushroom on blood pressure and lipid levels in spontaneously hypertensive rats (SHR). J Nutr Sci Vitaminol.(Tokyo) 1988;34(4):433-438. PubMed
  3. Kanmatsuse, K., Kajiwara, N., Hayashi, K., Shimogaichi, S., Fukinbara, I., Ishikawa, H., and Tamura, T. [Studies on Ganoderma lucidum. I. Efficacy against hypertension and side effects]. Yakugaku Zasshi 1985;105(10):942-947. PubMed
  4. Jin H, Zhang G, Cao X, and et al. Treatment of hypertension by linzhi combined with hypotensor and its effects on arterial, arteriolar and capillary pressure and microcirculation. In: Niimi H, Xiu RJ, Sawada T, and et al. Microcirculatory Approach to Asi

What These Ratings Mean

Every interaction above is graded three ways — here’s the key to each label.

Severity how clinically significant the interaction is
Major

Clinically significant. Avoid the combination, or use only under close professional supervision.

Moderate

Usually worth avoiding or managing — may need monitoring, a dose change, or timing apart.

Minor

Generally not serious. Be aware of it and mention it to your pharmacist.

Likelihood how strong the evidence is that the interaction actually happens in people
  • LikelyWell-controlled human studies have demonstrated the likely existence of this interaction.
  • ProbableInteraction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
  • PossibleInteraction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.
  • UnlikelyInteraction has been demonstrated in animal or in lab research but has been shown not to occur in humans.
Evidence the quality of the studies behind the rating (graded A–D)
  • AHigh-quality meta-analysis (quantitative systematic review).
  • BCase-control study.
  • CConsensus.
  • DAnecdotal evidence.

These ratings are for information only. Never start, stop, or otherwise change your therapy before speaking with your provider.

Keep it in perspective

Reishi Mushroom Also Interacts With Other Medications

Reishi Mushroom has 374 moderate known drug interactions in our database — the Phenoxybenzamine one above is one of them. If you take anything else, check it against the full list below.

Moderate 374 No known interaction 2,456 (incl. Phenoxybenzamine)
Taking anything else?

Check Another of Your Medications Against Reishi Mushroom

Covers the 2,830 medications we’ve checked against Reishi Mushroom. Pick one to open its full report.

Everything else you take

See Every Supplement That Interacts With Phenoxybenzamine

This page covers Reishi Mushroom only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Phenoxybenzamine page lists 137 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), American Hellebore (major), American Mistletoe (major), Tyramine (major) and Adrafinil (moderate).

By severity: 4 major · 112 moderate · 21 minor.

From our pharmacist’s overview on the Phenoxybenzamine page

“Phenoxybenzamine (Dibenzyline) is usually prescribed for pheochromocytoma, an adrenal tumor that sends blood pressure surging, often to steady a patient in the weeks before surgery, so keeping pressure in a narrow band is the entire goal of treatment. That makes this a list to treat carefully rather than skim.”

Reviewed by 2 · Jul 18, 2026

Open the Phenoxybenzamine interaction page

How much people look this up

Where Reishi Mushroom and Phenoxybenzamine Sit Against Everything Else

Out of every supplement and medication people look up on HelloPharmacist, here is where these two land this week — and which way each has been moving.

Supplement Reishi Mushroom
Top 10%

#95 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Phenoxybenzamine
Top half

#709 of 2,830 medications looked up here in the last 7 days

29 days ago today

Position among everything looked up on this site, not a measure of how commonly either one is used or how important it is. A supplement can climb this list because of a news story. It counts every request to the page, automated ones included, and nothing here identifies anyone.

Supplement

About Reishi Mushroom

What is Reishi Mushroom?

Reishi Mushroom
  • Immune support
  • Fatigue and general well-being
  • Stress and sleep
  • Inflammation
  • Heart and cholesterol health

Reishi is a traditional Asian mushroom widely used to support the immune system and overall wellness. Human evidence for most of its claimed benefits is limited or low-quality, so it should not replace proven treatments. It is generally well tolerated for short-term use, but check with your pharmacist or doctor before starting, especially if you are pregnant, nursing, or take other medicines.

Read the full Reishi Mushroom monograph & all interactions
Medication

About Phenoxybenzamine

What Is Phenoxybenzamine Used For?

Brand name: Dibenzyline

Phenoxybenzamine hydrochloride capsules are used to treat pheochromocytoma — a rare tumor of the adrenal gland that releases large bursts of stress hormones, causing dangerous spikes in blood pressure and heavy sweating. The capsules help keep those episodes under control.

If the heart rate becomes too fast during treatment, a doctor may also prescribe a beta-blocker alongside phenoxybenzamine.

See full Phenoxybenzamine drug information
Keep checking

Other Drugs & Reishi Mushroom

Browse every other medication we’ve checked against Reishi Mushroom — both the ones with a known interaction and the ones without. Select any drug for the full detail.

0Major
374Moderate
0Minor
2,455No known interaction
374 Moderate 2,455 No interaction
Moderate

374 interactions

Showing 60 of 374 moderate interactions — see all 374 on the Reishi Mushroom page.

No interaction 2,455 drugs checked — show the list

We also checked Reishi Mushroom against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 2,455 medications checked with no known interaction — see the full Reishi Mushroom list.

See the full Reishi Mushroom interactions page
See every supplement checked against Phenoxybenzamine, ranked by severity
Sources

Sources & How We Checked

Interaction details are evidence-graded and sourced from the Natural Medicines database. The medication overview comes from MedlinePlus.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

© 2021 Therapeutic Research Center, LLC

Keep exploring
Reishi Mushroom monograph › Uses, safety, and every drug interaction in one place Phenoxybenzamine supplement interactions › Every supplement checked against Phenoxybenzamine, ranked by severity Phenoxybenzamine drug information › The full plain-English guide to this medication Supplement interaction checker › Check any supplement or product against your medications Browse medications A–Z › Every drug we've checked against herbs & supplements Ask a pharmacist › Free, personal answer from our licensed team
Pharmacist Counseling Corner

Taking Reishi Mushroom and Phenoxybenzamine Together: Common Questions

Can you take Reishi Mushroom with Phenoxybenzamine?
There is a moderate interaction, so it may be acceptable with monitoring or timing changes — but check with your pharmacist first. Read the full details on this page and confirm with your pharmacist before combining them.
How serious is the Reishi Mushroom and Phenoxybenzamine interaction?
We rate it Moderate. This combination may require monitoring, a dose adjustment, or separating the times you take each one. Consult your pharmacist before using them together.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

Still Have a Question About Phenoxybenzamine and Reishi Mushroom?

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This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.