Drug & supplement interaction

Periwinkle + Cyclothiazide

Cyclothiazide brand names: Fluidil, Anhydron.

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

Periwinkle has a moderate interaction with Cyclothiazide. 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 Cyclothiazide

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

Moderate

ANTIHYPERTENSIVE DRUGS

Why this applies to Cyclothiazide

Cyclothiazide 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 simple version. Cyclothiazide is a thiazide-type water pill that lowers blood pressure by helping your body get rid of extra salt and fluid. Periwinkle contains a compound called vincamine, which lab and animal research suggests can relax and widen blood vessels, gently lowering blood pressure on its own.

Stack those two together and the worry is that your blood pressure could drop more than expected. That might leave you feeling dizzy, lightheaded, or woozy when you stand up, and in some folks it could lead to a fall. I'll be honest with you though: this is a theoretical concern based on how periwinkle behaves in studies, not strong human proof. Still, since both can lower pressure, it's worth a quick chat with your pharmacist or doctor 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 Cyclothiazide 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. Cyclothiazide)
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 Cyclothiazide

This page covers Periwinkle only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Cyclothiazide page lists 210 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), Asarabacca (major) and Dolomite (major).

By severity: 10 major · 175 moderate · 25 minor.

From our pharmacist’s overview on the Cyclothiazide page

“Cyclothiazide (Fluidil, Anhydron) is a thiazide diuretic for high blood pressure and fluid retention, and its 210 supplement interactions warrant real vigilance, especially the ten rated major. Most entries pull in one of two directions.”

Reviewed by 2 · Jul 18, 2026

Open the Cyclothiazide 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 Cyclothiazide 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 Cyclothiazide 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

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

29 days ago today
Medication Cyclothiazide
Top half

#1,099 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 Cyclothiazide, 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 Cyclothiazide supplement interactions › Every supplement checked against Cyclothiazide, 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 Cyclothiazide Together: Common Questions

Can you take Periwinkle with Cyclothiazide?
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 Cyclothiazide 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 Cyclothiazide 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.