Drug & supplement interaction

Periwinkle + Sitaxsentan sodium

Sitaxsentan sodium brand name: Thelin.

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

Periwinkle has a moderate interaction with Sitaxsentan sodium. Theoretically, taking periwinkle may increase the effects of antihypertensive drugs due to the hypotensive activity of vincamine, a constituent of periwinkle.

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

Periwinkle and Sitaxsentan sodium

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

Moderate

ANTIHYPERTENSIVE DRUGS

Why this applies to Sitaxsentan sodium

Sitaxsentan sodium falls under ANTIHYPERTENSIVE DRUGS — the group Periwinkle interacts with.

Theoretically, taking periwinkle may increase the effects of antihypertensive drugs due to the hypotensive activity of vincamine, a constituent of periwinkle.
Severity Moderate Likelihood Probable Evidence D

Interaction 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..

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

Here's the gist for Sitaxsentan (brand name Thelin), a medicine used to lower the high blood pressure in the lungs that comes with pulmonary arterial hypertension. Periwinkle contains a compound called vincamine, which on its own can gently relax blood vessels and nudge blood pressure downward. Pair it with sitaxsentan, which also works to widen vessels and lower pressure, and the two could add up.

If your blood pressure drops too far, you might feel dizzy, lightheaded, flushed, or unusually tired, especially when you stand up quickly. I'll be honest though, this concern is theoretical, based on how these compounds behave rather than real-world reports. Sitaxsentan isn't a prodrug, so this is about overlapping effects, not changed processing. Please check with your doctor or pharmacist before combining them.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. McGuffin M, Hobbs C, Upton R, Goldberg A, eds. American Herbal Products Association's Botanical Safety Handbook. Boca Raton, FL: CRC Press, LLC 1997.
  2. Brinker F. Herb Contraindications and Drug Interactions. 2nd ed. Sandy, OR: Eclectic Medical Publications, 1998.

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

Periwinkle Also Interacts With Other Medications

Periwinkle has 171 moderate known drug interactions in our database — the Sitaxsentan sodium one above is one of them. If you take anything else, check it against the full list below.

Moderate 171 No known interaction 2,659 (incl. Sitaxsentan sodium)
Taking anything else?

Check Another of Your Medications Against Periwinkle

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

Everything else you take

See Every Supplement That Interacts With Sitaxsentan sodium

This page covers Periwinkle only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Sitaxsentan sodium page lists 173 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 Siberian Cocklebur (major).

By severity: 7 major · 145 moderate · 21 minor.

From our pharmacist’s overview on the Sitaxsentan sodium page

“Sitaxsentan (Thelin) treats pulmonary arterial hypertension and carries a well known liver warning of its own, which is exactly why I read this list of 173 interacting supplements with genuine concern rather than a shrug. Most entries, 119 of them, either add to its blood pressure lowering effect or work against it, but the group I wou…”

Reviewed by 2 · Jul 18, 2026

Open the Sitaxsentan sodium interaction page

One more smart check

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

We hold 38 real supplement products containing Periwinkle, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Periwinkle. Your product may carry other ingredients that interact with Sitaxsentan sodium too, on top of Periwinkle — 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 Periwinkle and Sitaxsentan sodium 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 Periwinkle
Top half

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

29 days ago today
Medication Sitaxsentan sodium
Steady interest

#1,979 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 Periwinkle

What is Periwinkle?

  • Memory and cognitive support
  • Circulation problems
  • Dizziness and ringing in the ears
  • Minor wounds and sore throat (traditional)
  • High blood pressure (traditional)

Periwinkle (Vinca minor) is a flowering plant whose alkaloids are the source of vinpocetine, a compound marketed for memory and brain circulation. Evidence in humans is limited and mixed, and the plant contains potent compounds that can be toxic in larger amounts, so it should be used only with professional guidance. A closely related plant, Madagascar periwinkle, is the source of important cancer chemotherapy drugs but is not safe to use as a home remedy.

Read the full Periwinkle monograph & all interactions
Keep checking

Other Drugs & Periwinkle

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

0Major
171Moderate
0Minor
2,658No known interaction
171 Moderate 2,658 No interaction
Moderate

171 interactions

Showing 60 of 171 moderate interactions — see all 171 on the Periwinkle page.

No interaction 2,658 drugs checked — show the list

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

Showing the 60 most looked-up of 2,658 medications checked with no known interaction — see the full Periwinkle list.

See the full Periwinkle interactions page
See every supplement checked against Sitaxsentan sodium, 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
Periwinkle monograph › Uses, safety, and every drug interaction in one place Sitaxsentan sodium supplement interactions › Every supplement checked against Sitaxsentan sodium, 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 Periwinkle and Sitaxsentan sodium Together: Common Questions

Can you take Periwinkle with Sitaxsentan sodium?
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 Periwinkle and Sitaxsentan sodium 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 Sitaxsentan sodium and Periwinkle?

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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.