Drug & supplement interaction

Uva Ursi + Sirolimus

Sirolimus brand name: Rapamune.

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

Sirolimus falls into 2 drug categories that Uva Ursi can interact with; the most serious is rated moderate. Theoretically, uva ursi may decrease the metabolism of CYP3A4 substrates.

Read the full interaction report
SeverityModerate
LikelihoodPossible
Interactions2
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Uva Ursi and Sirolimus

These two interact in 2 distinct ways. Each one is explained separately below.

Why Are There 2 Interactions?

Uva Ursi interacts with whole categories of medication. Sirolimus falls into 2 of those categories, so it can interact with Uva Ursi in 2 different ways. We’ve listed each one below — your overall risk is driven by the most serious of them (Moderate).

Moderate

CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES

1 of 2

Why this applies to Sirolimus

Sirolimus falls under CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES — the group Uva Ursi interacts with.

Theoretically, uva ursi may decrease the metabolism of CYP3A4 substrates.
In vitro, uva ursi appears to inhibit CYP3A4. This effect has not been reported in humans.
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 with these two together. Your body relies on a liver enzyme called CYP3A4 to break down and clear sirolimus (Rapamune). In lab studies, uva ursi seems to slow that enzyme down. If that happened in real life, sirolimus could build up higher than intended, which can mean more side effects like mouth sores, swelling in the legs, high cholesterol, low blood counts, or kidney irritation.

The important caveat: this slowdown has only been seen in test-tube studies, not in actual people, so it's theoretical. Still, sirolimus is a drug where blood levels really matter, so I'd play it safe. Please check with your transplant team or pharmacist before adding uva ursi, since they can monitor your levels if needed.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Chauhan B, Yu C, Krantis A, et al. In vitro activity of uva-ursi against cytochrome P450 isoenzymes and P-glycoprotein. Can J Physiol Pharmacol. 2007;85(11):1099-107.
Minor

P-GLYCOPROTEIN SUBSTRATES

2 of 2

Sirolimus also falls under P-GLYCOPROTEIN SUBSTRATES.

Theoretically, uva ursi may alter the levels of drugs transported by P-glycoprotein.
In vitro, uva ursi appears to inhibit the multi-drug transporter protein, P-glycoprotein. This effect has not been reported in humans.
Severity Minor 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 short version: sirolimus (Rapamune) is moved around your body partly by a transporter called P-glycoprotein, which helps pump the drug out. In a lab dish, uva ursi seemed to slow that pump down. If that same thing happened in people, less sirolimus would get pumped out, so its levels could drift a bit higher than expected.

Now the important part: this has only been seen in test-tube studies, never in actual patients, so it's mostly theoretical. Still, sirolimus is a finicky transplant medicine where even small level changes matter, and too much can mean more side effects like mouth sores, swelling, or low blood counts. Please don't start or stop anything on your own. Just run uva ursi past your transplant team or pharmacist first.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Chauhan B, Yu C, Krantis A, et al. In vitro activity of uva-ursi against cytochrome P450 isoenzymes and P-glycoprotein. Can J Physiol Pharmacol. 2007;85(11):1099-107.

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

Uva Ursi Also Interacts With Other Medications

Uva Ursi has 741 moderate, 62 minor known drug interactions in our database — the Sirolimus one above is among them. If you take anything else, check it against the full list below.

Moderate 741 Minor 62 No known interaction 2,027 (incl. Sirolimus)
Taking anything else?

Check Another of Your Medications Against Uva Ursi

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

From our Q&A

Questions About Uva Ursi or Sirolimus

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Uva Ursi or Sirolimus, not necessarily both, but if one is close to what you were about to ask it will usually go further than a database entry can:

Not quite your question? Ask our pharmacists directly — it is free, there is no account required, and answers usually come back within 24 hours.

Everything else you take

See Every Supplement That Interacts With Sirolimus

This page covers Uva Ursi only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Sirolimus page lists 188 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Grapefruit (major), St. John's Wort (major), Acacia Rigidula (moderate) and Active Hexose Correlated Compound (ahcc) (moderate).

By severity: 3 major · 149 moderate · 36 minor.

From our pharmacist’s overview on the Sirolimus page

“Sirolimus (Rapamune) is the anti-rejection medicine transplant patients depend on, and it is a narrow-therapeutic-index drug, meaning small shifts in its blood level can invite rejection on one side or toxicity on the other. That is why the 188 supplements on this page deserve genuine wariness, starting with the three rated major.”

Reviewed by 2 · Jul 18, 2026

Open the Sirolimus interaction page

One more smart check

Taking Uva Ursi as Part of a Dietary Supplement Product? Check It for Interactions

We hold 1,423 real supplement products containing Uva Ursi, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Uva Ursi. Your product may carry other ingredients that interact with Sirolimus too, on top of Uva Ursi — 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 Uva Ursi and Sirolimus 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 Uva Ursi
Top 10%

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

29 days ago today
Medication Sirolimus
Top half

#1,044 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 Uva Ursi

What is Uva Ursi?

Uva Ursi
  • Urinary tract infections
  • Urinary discomfort
  • Mild diuretic
  • Kidney stones
  • Skin conditions

Uva ursi is a traditional herb used mainly for urinary tract infections, and its leaves contain a compound called arbutin that may have antimicrobial effects in the urine. Evidence in people is limited, and because high doses or long-term use may be harmful to the liver and could be toxic, it should only be used short-term and with guidance from a healthcare professional. Avoid it during pregnancy and breastfeeding.

Read the full Uva Ursi monograph & all interactions
Medication

About Sirolimus

What Is Sirolimus Used For?

Brand name: Rapamune

Oral sirolimus (tablets and oral solution) is used to prevent organ rejection in people aged 13 and older who have had a kidney transplant. It is also used to treat lymphangioleiomyomatosis (LAM), a rare lung disease.

Two other products contain sirolimus for different uses. Fyarro (given by IV) treats adults with advanced malignant perivascular epithelioid cell tumor (PEComa) that cannot be removed by surgery or has spread. Hyftor (a gel applied to the skin) treats facial angiofibroma linked to tuberous sclerosis in people 6 years and older.

See full Sirolimus drug information Sirolimus NDC codes and packages
Keep checking

Other Drugs & Uva Ursi

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

0Major
741Moderate
62Minor
2,026No known interaction
741 Moderate 62 Minor 2,026 No interaction
Moderate

741 interactions

Showing 60 of 741 moderate interactions — see all 741 on the Uva Ursi page.

Minor

62 interactions

Showing 60 of 62 minor interactions — see all 62 on the Uva Ursi page.

No interaction 2,026 drugs checked — show the list

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

Showing the 60 most looked-up of 2,026 medications checked with no known interaction — see the full Uva Ursi list.

See the full Uva Ursi interactions page
See every supplement checked against Sirolimus, 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
Uva Ursi monograph › Uses, safety, and every drug interaction in one place Sirolimus supplement interactions › Every supplement checked against Sirolimus, ranked by severity Sirolimus drug information › The full plain-English guide to this medication Sirolimus NDC codes and packages › Every package, labeler and price in the FDA directory 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 Uva Ursi and Sirolimus Together: Common Questions

Can you take Uva Ursi with Sirolimus?
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 2 interactions listed for Uva Ursi and Sirolimus?
Sirolimus belongs to more than one drug category, and Uva Ursi 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 Uva Ursi and Sirolimus 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 Sirolimus and Uva Ursi?

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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.