Drug & supplement interaction

Madagascar Periwinkle + Isoniazid, Rifampin

Isoniazid, Rifampin brand name: Rifamate.

No Known Interaction
Medically reviewed by · Updated July 2026 · Pair last verified Sep 13, 2026
The bottom line No known interaction

We found no known interaction between Madagascar Periwinkle and Isoniazid, Rifampin in our sources. Absence of a documented interaction is not the same as proven safety, and does not guarantee one does not exist. Do not start, stop, or change a medication or supplement based on this page; confirm with your pharmacist or doctor first.

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Interaction report

Madagascar Periwinkle and Isoniazid, Rifampin

We checked these two against our interaction database. Here is what we found.

No Known Interaction Found

We did not find a documented interaction between Isoniazid, Rifampin and Madagascar Periwinkle in our sources. This does not guarantee that the combination is completely free of risk — there is often limited research on supplements and herbal products, especially around drug interactions.

If you decide to take both, the practical routine is simple: add one new thing at a time and note the date you started it. If the combination is going to disagree with you, it usually shows in the first days to a couple of weeks — and a start date turns “I’ve been feeling off” into something a pharmacist can actually work with. Do not stop a prescribed medicine on your own.

Always talk with your pharmacist or doctor before making changes to your medications or supplements, particularly if you take several medications or have an ongoing health condition.

Madagascar Periwinkle safety at a glance

Madagascar Periwin... overall Avoid The raw plant contains toxic alkaloids and is not considered safe as a self-care supplement.
Pregnancy Likely Unsafe When used orally. Madagascar periwinkle has abortifacient and teratogenic properties. Read the full pregnancy detail
Breastfeeding Likely Unsafe When used orally; avoid using. Read the full breastfeeding detail

Pregnancy & breastfeeding ratings are from Natural Medicines (Therapeutic Research Center) — the full detail is in the Special populations card below. Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

Still wondering about combining Isoniazid, Rifampin and Madagascar Periwinkle? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
How we checked

Why No Interaction Is Listed for Isoniazid, Rifampin

Interactions in our licensed database are recorded against drug classes, not just single drug names. Isoniazid, Rifampin is filed under 16 classifications — including cytochrome p450 2c9 (cyp2c9) inducers, organic anion-transporting polypeptide substrates (oatp), cytochrome p450 2c19 (cyp2c19) inhibitors. Madagascar Periwinkle has documented interactions with 2 drug classes — the most serious being antidiabetes drugs (moderate) and lithium (moderate) — and none of Isoniazid, Rifampin’s classifications are among them.

Classification data comes from our licensed Natural Medicines dataset. A medication can belong to classes beyond those recorded there, so this describes how the check was run — it is not a safety guarantee.

Keep it in perspective

Madagascar Periwinkle Does Interact With Other Medications

Madagascar Periwinkle has 87 moderate known drug interactions in our database — Isoniazid, Rifampin isn’t one of them. If you take anything else, check it against the full list below.

Moderate 87 No known interaction 2,743 (incl. Isoniazid, Rifampin)
Taking anything else?

Check Another of Your Medications Against Madagascar Periwinkle

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

What to actually watch for

What Madagascar Periwinkle Itself Has Been Linked To

This is not an interaction — nothing below involves Isoniazid, Rifampin. It is the side-effect record for Madagascar Periwinkle on its own, from the licensed Natural Medicines monograph. If something new turns up after you add Madagascar Periwinkle, this list is the first place to look. 3 entries are worth acting on rather than waiting out — marked below.

  • Hallucinations / Seizures Worth acting on Additional detail

    “Orally, Madagascar periwinkle is generally regarded as unsafe for use. Any benefits of therapy may not outweigh the risk of toxicity. Madagascar periwinkle can cause hallucinations, seizures, gastrointestinal upset, hepatotoxicity, and alopecia (17).”

    Madagascar Periwinkle · Natural Medicines adverse-effect record, reported in alopecia.

    4 sources cited
    1. 17. Ellenhorn MJ, et al. Ellenhorn's Medical Toxicology: Diagnoses and Treatment of Human Poisoning. 2nd ed. Baltimore, MD: Williams & Wilkins, 1997.
    2. 6. The Review of Natural Products by Facts and Comparisons. St. Louis, MO: Wolters Kluwer Co., 1999.
    3. 15. McEvoy GK, ed. AHFS Drug Information. Bethesda, MD: American Society of Health-System Pharmacists, 1998.
    4. 100665. Ghosh D, Roy I, Chanda S, Gupta-Bhattacharya S. Allergy to periwinkle pollen (Catharanthus roseus G. Don.). Ann Agric Environ Med. 2007;14(1):39-43.

    “Orally, Madagascar periwinkle can cause hallucinations and seizures (17). The vinca alkaloid constituents of Madagascar periwinkle have been reported to cause dizziness, vertigo, and neurotoxicity (6,15).”

    Madagascar Periwinkle · Natural Medicines adverse-effect record, reported in epilepsy.

    3 sources cited
    1. 17. Ellenhorn MJ, et al. Ellenhorn's Medical Toxicology: Diagnoses and Treatment of Human Poisoning. 2nd ed. Baltimore, MD: Williams & Wilkins, 1997.
    2. 6. The Review of Natural Products by Facts and Comparisons. St. Louis, MO: Wolters Kluwer Co., 1999.
    3. 15. McEvoy GK, ed. AHFS Drug Information. Bethesda, MD: American Society of Health-System Pharmacists, 1998.
  • A low platelet count / A low white blood cell count / Bleeding or bruising Worth acting on Additional detail

    “Orally, the vinca alkaloid constituents of Madagascar periwinkle have been reported to cause leukopenia, thrombocytopenia, bleeding, and hyperuricemia (6,15).”

    Madagascar Periwinkle · Natural Medicines adverse-effect record, reported in leukopenia.

    2 sources cited
    1. 6. The Review of Natural Products by Facts and Comparisons. St. Louis, MO: Wolters Kluwer Co., 1999.
    2. 15. McEvoy GK, ed. AHFS Drug Information. Bethesda, MD: American Society of Health-System Pharmacists, 1998.
  • Liver problems / An allergic reaction Worth acting on Additional detail

    Recorded for Madagascar Periwinkle in the same Natural Medicines adverse-effect record shown under Hallucinations / Seizures above.

  • Hair loss Additional detail

    “Orally, Madagascar periwinkle can cause alopecia (17).”

    Madagascar Periwinkle · Natural Medicines adverse-effect record, reported in alopecia.

    1 source cited
    1. 17. Ellenhorn MJ, et al. Ellenhorn's Medical Toxicology: Diagnoses and Treatment of Human Poisoning. 2nd ed. Baltimore, MD: Williams & Wilkins, 1997.
  • Stomach upset Additional detail

    “Orally, Madagascar periwinkle can cause gastrointestinal upset (17). The vinca alkaloid constituents of Madagascar periwinkle have been reported to cause nausea and vomiting (6,15).”

    Madagascar Periwinkle · Natural Medicines adverse-effect record, reported in nausea and vomiting.

    3 sources cited
    1. 17. Ellenhorn MJ, et al. Ellenhorn's Medical Toxicology: Diagnoses and Treatment of Human Poisoning. 2nd ed. Baltimore, MD: Williams & Wilkins, 1997.
    2. 6. The Review of Natural Products by Facts and Comparisons. St. Louis, MO: Wolters Kluwer Co., 1999.
    3. 15. McEvoy GK, ed. AHFS Drug Information. Bethesda, MD: American Society of Health-System Pharmacists, 1998.
  • Dizziness Additional detail

    Recorded for Madagascar Periwinkle in the same Natural Medicines adverse-effect record shown under Hallucinations / Seizures above.

Showing the 10 most notable of 12 recorded effects — ranked by how unusual each one is across medicines generally, with serious effects weighted up.

Everything above comes from the Natural Medicines adverse-effect record for Madagascar Periwinkle — expand a row for the licensed statement it rests on. We haven’t matched Isoniazid, Rifampin to its FDA label in our system yet, so we can’t compare its own side-effect list here — the leaflet that comes with your prescription is the authoritative list for Isoniazid, Rifampin.

Special populations

Madagascar Periwinkle in Pregnancy & Breastfeeding

Pregnancy Likely Unsafe

When used orally. Madagascar periwinkle has abortifacient and teratogenic properties.

Lactation Likely Unsafe

When used orally; avoid using.

DISCLAIMER: This tool is intended for informational purposes only, and should not be interpreted as specific medical advice. Patients should consult with a qualified healthcare provider before making decisions about therapies and/or health conditions.© 2026 Therapeutic Research Center

Everything else you take

See Every Supplement That Interacts With Isoniazid, Rifampin

This page covers Madagascar Periwinkle only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Isoniazid, Rifampin page lists 145 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Apple (major), Asarabacca (major), Beer (major) and Grapefruit (major).

By severity: 8 major · 117 moderate · 20 minor.

From our pharmacist’s overview on the Isoniazid, Rifampin page

“Rifamate combines isoniazid and rifampin, the backbone of tuberculosis treatment, and both drugs are hard on the liver, which is why this list of 145 supplement and herbal interactions deserves genuine respect. Eight entries rate major, and the largest cluster, 38 ingredients, adds to that same liver strain, with alcohol in beer or win…”

Reviewed by 2 · Jul 18, 2026

Open the Isoniazid, Rifampin interaction page

One more smart check

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

We hold 8 real supplement products containing Madagascar Periwinkle, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Madagascar Periwinkle. Even though Madagascar Periwinkle itself has no known interaction with Isoniazid, Rifampin, another ingredient on your label might. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Madagascar Periwinkle and Isoniazid, Rifampin 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 Madagascar Periwinkle
Top half

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

29 days ago today
Medication Isoniazid, Rifampin
Top 5%

#110 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.

Where does our data come from?
  • Source: the Natural Medicines (TRC Healthcare) clinical database — the evidence-graded professional reference for herb & supplement interactions.
  • Citation library: 103,510 references behind our interaction content, 65,311 of them resolved to verified PubMed/DOI sources. See every Madagascar Periwinkle reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 13, 2026. The Madagascar Periwinkle and Isoniazid, Rifampin records this page draws on were last updated July 11, 2026.
  • What “no known interaction” means: no documented interaction in the sources above — not a guarantee of safety. Supplements are studied far less than prescription drugs, so we say exactly what the evidence supports, and nothing more.
Data structure & sourcing designed and verified by .
Supplement

About Madagascar Periwinkle

What is Madagascar Periwinkle?

  • Diabetes (folk use)
  • High blood pressure (traditional use)
  • Sore throat and mouth ailments
  • Wound healing (topical)
  • Source of cancer chemotherapy drugs

Madagascar periwinkle is a flowering plant famous as the natural source of important chemotherapy drugs (vincristine and vinblastine), but the raw plant itself is toxic and not safe to use as a home remedy. While it has a long history in traditional medicine, there is no reliable evidence that taking the whole herb is safe or effective, and it should not be self-administered.

Catharanthus roseus · Apocynaceae · Leaves, roots, and whole aerial parts · Capsules, dried herb, teas, tinctures, and topical extracts (pharmaceutical drugs are made from purified alkaloids)

An interaction check asks whether these two react with each other — it does not ask whether Madagascar Periwinkle is a good idea for someone in your situation. Here is what our Madagascar Periwinkle record says about it on its own.

Madagascar Periwinkle: dosing

There is no established safe dose for Madagascar periwinkle as a dietary supplement, and because the plant is toxic, we do not recommend using it for self-care.The medicines made from this plant (such as vincristine and vinblastine) are prescription chemotherapy drugs that must be dosed and administered by trained healthcare providers in a clinical setting. In most cases, the safest choice is to avoid the raw herb entirely.

From our Madagascar Periwinkle monograph — the full record covers uses, side effects and every documented interaction.

Read the full Madagascar Periwinkle monograph & all interactions
Keep checking

Other Drugs & Madagascar Periwinkle

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

0Major
87Moderate
0Minor
2,742No known interaction
87 Moderate 2,742 No interaction
Moderate

87 interactions

Showing 60 of 87 moderate interactions — see all 87 on the Madagascar Periwinkle page.

No interaction 2,742 drugs checked — show the list

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

Showing the 60 most looked-up of 2,742 medications checked with no known interaction — see the full Madagascar Periwinkle list.

See the full Madagascar Periwinkle interactions page
See every supplement checked against Isoniazid, Rifampin, ranked by severity
Evidence & sources

Madagascar Periwinkle References

The 6 references that drive our Madagascar Periwinkle monograph and interaction data, from the evidence-graded Natural Medicines (TRC Healthcare) database. Citations with a link open the study on PubMed or the publisher’s site.

  1. The Review of Natural Products by Facts and Comparisons. St. Louis, MO: Wolters Kluwer Co., 1999.
  2. McEvoy GK, ed. AHFS Drug Information. Bethesda, MD: American Society of Health-System Pharmacists, 1998.
  3. Ellenhorn MJ, et al. Ellenhorn's Medical Toxicology: Diagnoses and Treatment of Human Poisoning. 2nd ed. Baltimore, MD: Williams & Wilkins, 1997.
  4. Brinker F. Herb Contraindications and Drug Interactions. 2nd ed. Sandy, OR: Eclectic Medical Publications, 1998.
  5. Ghosh D, Roy I, Chanda S, Gupta-Bhattacharya S. Allergy to periwinkle pollen (Catharanthus roseus G. Don.). Ann Agric Environ Med. 2007;14(1):39-43.
  6. Oguntibeju OO, Aboua Y, Goboza M. Vindoline-A natural product from catharanthus roseus reduces hyperlipidemia and renal pathophysiology in experimental type 2 diabetes. Biomedicines. 2019 Aug 13;7(3):59. PubMed

Medication overviews come from MedlinePlus (NIH); supplement label data from the NIH Dietary Supplement Label Database. Content is written and reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.

Pharmacist Counseling Corner

Taking Madagascar Periwinkle and Isoniazid, Rifampin Together: Common Questions

Is it safe to take Madagascar Periwinkle with Isoniazid, Rifampin?
We do not list a known interaction between Madagascar Periwinkle and Isoniazid, Rifampin. That does not guarantee the combination is risk-free, so confirm with your pharmacist or doctor — especially if you take other medications or have a health condition.
How was the Madagascar Periwinkle and Isoniazid, Rifampin combination checked?
Interactions in our licensed database are recorded against drug classes. Isoniazid, Rifampin is filed under 16 classifications, and Madagascar Periwinkle has documented interactions with 2 drug classes — none of Isoniazid, Rifampin's classifications are among them. A medication can belong to classes beyond those recorded in our dataset, so this describes how the check was run rather than guaranteeing safety.
Does Madagascar Periwinkle interact with any other medications?
Yes. Madagascar Periwinkle has 87 documented drug interactions in our database — Isoniazid, Rifampin is simply not one of them. If you take anything else, it is worth checking each one; they are all listed on this page.
Does Isoniazid, Rifampin interact with any supplements?
Yes. Isoniazid, Rifampin has documented interactions with 145 supplements in our database — Madagascar Periwinkle is not one of them. The Isoniazid, Rifampin interaction page linked on this page lists every one, ranked by severity.

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

Where next

Keep Exploring

Madagascar Periwinkle monograph Uses, safety profile, and every drug interaction in one place Isoniazid, Rifampin supplement interactions Every supplement checked against Isoniazid, Rifampin, 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 References The 6 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Isoniazid, Rifampin and Madagascar 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.