Drug & supplement interaction

Oregon Grape + Macitentan, Tadalafil

Macitentan, Tadalafil brand name: Opsynvi.

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

Macitentan, Tadalafil falls into 3 drug categories that Oregon Grape can interact with; the most serious is rated moderate. Theoretically, Oregon grape might increase the risk of hypotension when taken with antihypertensive drugs.

Read the full interaction report
SeverityModerate
LikelihoodPossible
Interactions3
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Oregon Grape and Macitentan, Tadalafil

These two interact in 3 distinct ways. Each one is explained separately below.

Why Are There 3 Interactions?

Oregon Grape interacts with whole categories of medication. Macitentan, Tadalafil falls into 3 of those categories, so it can interact with Oregon Grape in 3 different ways. We’ve listed each one below — your overall risk is driven by the most serious of them (Moderate).

Moderate

ANTIHYPERTENSIVE DRUGS

1 of 3

Why this applies to Macitentan, Tadalafil

Macitentan, Tadalafil falls under ANTIHYPERTENSIVE DRUGS — the group Oregon Grape interacts with.

Theoretically, Oregon grape might increase the risk of hypotension when taken with antihypertensive drugs.
Animal research suggests that berberine, a constituent of Oregon grape, can have hypotensive effects. Also, an analysis of clinical evidence suggests that taking berberine in combination with amlodipine (Norvasc) can lower systolic and diastolic blood pressure when compared with taking amlodipine alone.
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

Opsynvi combines two blood pressure lowering medicines: macitentan (which relaxes blood vessels in the lungs) and tadalafil (the same active ingredient as Cialis). Both can already lower your blood pressure. Oregon grape contains berberine, and in lab and animal studies berberine also seems to nudge blood pressure down. So the concern here is simple math: stacking them could add up to a bigger drop than expected.

If your pressure dips too low, you might feel dizzy, lightheaded, flushed, headachy, or wobbly when you stand up. Keep in mind this interaction is theoretical, mostly based on animal data, so it may not amount to much in real life. Still, since Opsynvi is powerful on its own, please check with your pharmacist or doctor before adding Oregon grape.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Sabir M and Bhide NK. Study of some pharmacological actions of berberine. Ind J Physiol & Pharmac 1971;15(3):111-132.
  2. Chun YT, Yip TT, Lau KL, and et al. A biochemical study on the hypotensive effect of berberine in rats. Gen Pharmac 1979;10:177-182. PubMed
  3. Lan J, Zhao Y, Dong F, et al. Meta-analysis of the effect and safety of berberine in the treatment of type 2 diabetes mellitus, hyperlipemia and hypertension. J Ethnopharmacol. 2015;161:69-81. PubMed
Moderate

CYTOCHROME P450 2C9 (CYP2C9) SUBSTRATES

2 of 3

Macitentan, Tadalafil also falls under CYTOCHROME P450 2C9 (CYP2C9) SUBSTRATES.

Theoretically, Oregon grape might increase serum levels of drugs metabolized by CYP2C9.
Preliminary clinical evidence suggests that berberine, a constituent of Oregon grape, can inhibit cytochrome P450 2C9 (CYP2C9).
Severity Moderate Likelihood Possible Evidence B

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 for Opsynvi, which combines macitentan and tadalafil. The berberine in Oregon grape may block a liver enzyme called CYP2C9, which helps clear these medicines. If that enzyme slows down, more of the drug can linger in your body, which could nudge up its usual side effects. With this combo, that might mean more low blood pressure, dizziness, headaches, flushing, or nasal congestion.

Now, the honest part: this is mostly theoretical, based on limited lab and early clinical data, so it's not a sure thing. Still, blood pressure medicines aren't something to gamble with. Before adding an Oregon grape supplement, please check with your pharmacist or doctor so they can weigh it for you.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Guo, Y., Chen, Y., Tan, Z. R., Klaassen, C. D., and Zhou, H. H. Repeated administration of berberine inhibits cytochromes P450 in humans. Eur J Clin Pharmacol 2012;68(2):213-217. PubMed
Moderate

CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES

3 of 3

Macitentan, Tadalafil also falls under CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES.

Theoretically, Oregon grape might increase serum levels of drugs metabolized by CYP3A4.
In vitro research and preliminary clinical evidence suggest that berberine, a constituent of Oregon grape, moderately inhibits cytochrome P450 3A4 (CYP3A4).
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

Opsynvi is a combo pill of two medicines used for pulmonary arterial hypertension, and both macitentan and tadalafil are broken down largely by a liver enzyme called CYP3A4. The berberine in Oregon grape may gently slow that enzyme down. If it does, these drugs could linger a bit longer in your body, nudging their levels up. In real life that might show up as more headache, flushing, low blood pressure, dizziness, a stuffy nose, or leg swelling.

Keep in mind this is a theoretical concern based mostly on lab work, so I don't want to alarm you. Concentrated berberine supplements are more likely to matter than a tiny amount. Please run it by your pharmacist or doctor before combining them.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Wu X, Li Q, Xin H, Yu A, Zhong M. Effects of berberine on the blood concentration of cyclosporin A in renal transplanted recipients: clinical and pharmacokinetic study. Eur J Clin Pharmacol 2005;61:567-72. PubMed
  2. Budzinski JW, Foster BC, Vandenhoek S, Arnason JT. An in vitro evaluation of human cytochrome P450 3A4 inhibition by selected commercial herbal extracts and tinctures. Phytomedicine 2000;7:273-82. PubMed
  3. Guo, Y., Chen, Y., Tan, Z. R., Klaassen, C. D., and Zhou, H. H. Repeated administration of berberine inhibits cytochromes P450 in humans. Eur J Clin Pharmacol 2012;68(2):213-217. PubMed
  4. Hermann, R. and von, Richter O. Clinical evidence of herbal drugs as perpetrators of pharmacokinetic drug interactions. Planta Med 2012;78(13):1458-1477. PubMed

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

Oregon Grape Also Interacts With Other Medications

Oregon Grape has 1,217 moderate known drug interactions in our database — the Macitentan, Tadalafil one above is among them. If you take anything else, check it against the full list below.

Moderate 1,217 No known interaction 1,613 (incl. Macitentan, Tadalafil)
Taking anything else?

Check Another of Your Medications Against Oregon Grape

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

Everything else you take

See Every Supplement That Interacts With Macitentan, Tadalafil

This page covers Oregon Grape only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Macitentan, Tadalafil page lists 264 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), Beer (major) and Grapefruit (major).

By severity: 10 major · 215 moderate · 39 minor.

From our pharmacist’s overview on the Macitentan, Tadalafil page

“Opsynvi pairs macitentan and tadalafil to lower pressure in the lung arteries, so anything that drops blood pressure further or shifts how the body handles these drugs deserves genuine respect, and I would read this list carefully. Ten of the 264 ingredients rate major, and most of the rest fall into two camps: additive blood-pressure-…”

Reviewed by 2 · Jul 18, 2026

Open the Macitentan, Tadalafil interaction page

One more smart check

Taking Oregon Grape as Part of a Dietary Supplement Product? Check It for Interactions

We hold 740 real supplement products containing Oregon Grape, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Oregon Grape. Your product may carry other ingredients that interact with Macitentan, Tadalafil too, on top of Oregon Grape — and those would not show on this page. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Oregon Grape and Macitentan, Tadalafil 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 Oregon Grape
Top 25%

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

29 days ago today
Medication Macitentan, Tadalafil
Top half

#1,317 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 Oregon Grape

What is Oregon Grape?

Oregon Grape
  • Psoriasis (topical)
  • Eczema and other skin conditions
  • Digestive upset
  • Mild skin infections
  • General 'detox' or tonic use

Oregon grape is a shrub whose root contains berberine and related compounds. The strongest (though still modest) evidence is for topical creams that may slightly ease psoriasis; evidence for other uses is limited. Talk with your pharmacist or doctor before using it, and avoid it during pregnancy and breastfeeding.

Read the full Oregon Grape monograph & all interactions
Keep checking

Other Drugs & Oregon Grape

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

0Major
1,217Moderate
0Minor
1,612No known interaction
1,217 Moderate 1,612 No interaction
Moderate

1,217 interactions

Showing 60 of 1,217 moderate interactions — see all 1,217 on the Oregon Grape page.

No interaction 1,612 drugs checked — show the list

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

Showing the 60 most looked-up of 1,612 medications checked with no known interaction — see the full Oregon Grape list.

See the full Oregon Grape interactions page
See every supplement checked against Macitentan, Tadalafil, 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
Oregon Grape monograph › Uses, safety, and every drug interaction in one place Macitentan, Tadalafil supplement interactions › Every supplement checked against Macitentan, Tadalafil, ranked by severity 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 Oregon Grape and Macitentan, Tadalafil Together: Common Questions

Can you take Oregon Grape with Macitentan, Tadalafil?
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.
Why are there 3 interactions listed for Oregon Grape and Macitentan, Tadalafil?
Macitentan, Tadalafil belongs to more than one drug category, and Oregon Grape interacts with each of those categories a little differently. We list every one so nothing is missed — your overall risk is driven by the most serious of them.
How serious is the Oregon Grape and Macitentan, Tadalafil 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 Macitentan, Tadalafil and Oregon Grape?

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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.