Herb & supplement monograph

Madagascar Periwinkle Drug Interactions, Uses, Safety & More

Medically reviewed by ·Updated July 2026
What is this page for?

First and foremost: how Madagascar Periwinkle interacts with medications. The heart of this page is the interaction list — every drug Madagascar Periwinkle is known to interact with, and how serious each one is.

But these pages have grown well beyond that into a full monograph — what Madagascar Periwinkle is, what people use it for and how strong the evidence is, its safety and side effects, and answers to the questions we’re asked most — written and reviewed by the clinical staff at HelloPharmacist. It’s educational information from our licensed clinical databases, not medical advice, and we don’t sell or endorse products. Our editorial policy

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Madagascar Periwinkle Drug Interactions: The Bottom Line

From the HelloPharmacist Editorial Team · Updated July 2026

Based on the available evidence, the overall risk of a clinically significant Madagascar Periwinkle drug interaction appears low for most people, though a few closely monitored medicines deserve some care. None of the listed interactions are rated major, and every one is graded moderate with only theoretical or animal-based evidence behind it.

Interactions deserving the most attention

The combinations most worth watching involve diabetes medications and lithium. Animal research suggests Madagascar periwinkle can lower blood sugar, so pairing it with diabetes medicines could theoretically add to their effect, and blood sugar changes matter for anyone whose glucose is tightly managed. The plant is also thought to act as a mild diuretic, which could in theory raise lithium levels, a medicine with a narrow safety margin. Neither concern has been confirmed in human studies.

What the rest of the list means

The long list of interacting medications largely reflects these two broad drug groups. All of the concerns are theoretical, drawn from animal or lab findings rather than documented problems in people, so a listed interaction does not mean the combination has been shown to cause harm.

Check your medications against Madagascar Periwinkle

Based on HelloPharmacist’s Madagascar Periwinkle interaction data and reviewed under our editorial standards.

Interaction report

Drugs that interact with Madagascar Periwinkle

87 medications have a known interaction with Madagascar Periwinkle, graded by severity. Select any drug for the full evidence-based detail.

2,830 drugs
AcarboseGlucobay, Prandase, Precose› AcetohexamideDymelor› AlbiglutideTanzeum› AlogliptinNesina› Alogliptin, MetforminKazano› Alogliptin, PioglitazoneOseni› Antidiabetes, Dipeptidyl Peptidase-4 (dpp-iv) InhibitorGlyxambi› CanagliflozinInvokana› Canagliflozin, MetforminInvokamet› Canagliflozin, Metformin HydrochlorideInvokamet XR› ChlorpropamideChlorpropam, Diabinese› DapagliflozinFarxiga› Dapagliflozin Propanediol, MetforminXigduo XR› Dapagliflozin Propanediol, Saxagliptin HydrochlorideQtern› Dapagliflozin, Metformin Hydrochloride, Saxagliptin HydrochlorideQternmet XR› Dasiglucagon HydrochlorideZegalogue› DulaglutideTrulicity› EmpagliflozinJardiance› Empagliflozin, Linagliptin, Metformin HydrochlorideTrijardy XR› Empagliflozin, MetforminSynjardy› Empagliflozin, Metformin HydrochlorideSynjardy XR› ErtugliflozinSteglatro› Ertugliflozin, Metformin HydrochlorideSegluromet› ExenatideBydureon, Byetta› Exenatide SyntheticBydureon BCISE› GliclazideDiamicron› GlimepirideAmaryl› GlipizideGlucotrol, Glucotrol XL› Glipizide, MetforminMetaglip› GlucagonBaqsimi, Glucagon›
Read The List Like a Pharmacist

What Severity, Likelihood & Evidence Mean

Severity — How Serious It Can Be

  • Major. Clinically significant; generally best avoided, or used only under direct professional supervision.
  • Moderate. May need monitoring, a dose adjustment, or separating the times you take each one.
  • Minor. Generally not clinically significant, but still worth noting and mentioning to your pharmacist.
  • No known interaction. Checked against our sources with nothing documented — not the same as proven safety.

Likelihood — How Well It’s Documented

  • Likely. Well-controlled human studies have demonstrated the likely existence of this interaction
  • Probable. 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.
  • Possible. 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
  • Unlikely. Interaction has been demonstrated in animal or in lab research but has been shown not to occur in humans.

Where This Data Comes From

  • Interaction records are evidence-graded and sourced from the Natural Medicines database (TRC Healthcare), the same reference used by pharmacists and hospitals.
  • Each drug listed above links to the full report for that exact Madagascar Periwinkle combination — clinical detail, likelihood, evidence level, and citations.
  • Content is reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.
The big picture

The kinds of drugs Madagascar Periwinkle affects

Every type of medication (drug category) Madagascar Periwinkle is known to interact with. Open any category for the detail — or search your exact drug in the checker above.

All 2 drug categories Madagascar Periwinkle interacts with
Antidiabetes DrugsLithium
Antidiabetes Drugs

Animal research shows that Madagascar periwinkle lowers blood glucose levels in diabetic rats. Theoretically, using Madagascar periwinkle in combination with antidiabetes drugs might increase the risk of hypoglycemia; monitor blood glucose closely.

Likelihood Possible Evidence D
Lithium

Madagascar periwinkle is thought to have diuretic properties. Theoretically, due to these potential diuretic effects, Madagascar periwinkle might reduce excretion and increase levels of lithium. The dose of lithium might need to be decreased.

Likelihood Possible Evidence D
Monograph

Madagascar Periwinkle: Uses, Safety & Side Effects

Medically reviewed by · Reviewed July 2026 ·
The bottom line

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.

Scientific name
Catharanthus roseus
Family
Apocynaceae
Part used
Leaves, roots, and whole aerial parts
Common forms
Capsules, dried herb, teas, tinctures, and topical extracts (pharmaceutical drugs are made from purified alkaloids)
People commonly use it for
  • Diabetes (folk use)
  • High blood pressure (traditional use)
  • Sore throat and mouth ailments
  • Wound healing (topical)
  • Source of cancer chemotherapy drugs

Popular and traditional uses — not proof it works. See “Uses & effectiveness” below for the evidence.

Safety at a glance
OverallBest avoided

The raw plant contains toxic alkaloids and is not considered safe as a self-care supplement.

PregnancyLikely Unsafe

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

Read the full pregnancy detail
BreastfeedingLikely Unsafe

When used orally; avoid using.

Read the full breastfeeding detail

Pregnancy & breastfeeding ratings are from Natural Medicines (Therapeutic Research Center). Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

Jump to a section

Overview

Madagascar periwinkle (Catharanthus roseus) is a small evergreen flowering plant with pink or white blooms. As the name suggests, it is native to Madagascar, but it now grows in warm regions all over the world and is often planted as an ornamental garden flower.

The plant has a long history in traditional medicine across many cultures, where it has been used for conditions such as diabetes, high blood pressure, and minor infections. Its biggest claim to fame, however, is in modern medicine: scientists discovered that it contains compounds used to make powerful chemotherapy drugs.

It is important to understand the difference between the purified, prescription drugs made from this plant and the raw herb itself. The drugs are carefully measured and given by medical professionals. The whole plant is toxic and is not a safe home remedy.

Uses & effectiveness

People have traditionally used Madagascar periwinkle for a wide range of problems, including diabetes, high blood pressure, sore throats, and to help heal wounds. Despite this long history, there is not enough reliable human evidence to show that the raw herb safely and effectively treats any of these conditions.

The plant's most proven value is as a raw material for medicine. Two of its natural compounds, vincristine and vinblastine, are purified and used as approved chemotherapy drugs to treat cancers such as leukemia and lymphoma. This is a major medical achievement, but it does not mean drinking periwinkle tea or taking the herb will treat cancer or any other illness.

Because the plant is toxic, the small amount of research on the whole herb does not support using it for self-treatment. People interested in its benefits should rely only on FDA-approved medications prescribed by a doctor.

How it works

Madagascar periwinkle contains a large group of natural compounds called vinca alkaloids, including vincristine and vinblastine. In laboratory studies, these compounds interfere with the way cells divide, which is why purified versions are useful in stopping fast-growing cancer cells.

The plant also contains other alkaloids that have been studied in animals and lab settings for possible effects on blood sugar and blood pressure. However, these findings are mostly preliminary and come from laboratory or animal research, not well-designed human studies.

The same alkaloids that make the plant medically useful also make it toxic. This is why the active ingredients must be extracted, purified, and carefully dosed in a pharmaceutical setting rather than taken as a raw herb.

Safety & precautions

The raw Madagascar periwinkle plant is considered toxic and should not be used as a home supplement. Eating the plant or taking unregulated extracts can cause serious poisoning.

People with existing health conditions, those taking other medications, and anyone considering it for a serious illness like cancer or diabetes should never try to self-treat with this plant. The purified drugs made from it require close medical supervision because they can cause significant side effects even when properly dosed.

Pregnancy and breastfeeding: Avoid Madagascar periwinkle completely if you are pregnant or breastfeeding. The toxic alkaloids may harm a developing baby or pass into breast milk, and there is no safe established dose.

Side effects

Taking the raw plant can cause toxic effects such as nausea, vomiting, stomach upset, dizziness, low blood pressure, and damage to nerves. In larger amounts it can affect the blood and nervous system and cause serious harm.

The purified chemotherapy drugs made from this plant are known to cause side effects like nerve damage (tingling, numbness, or weakness), low blood cell counts, hair loss, and constipation. These drugs are only given under medical supervision with monitoring.

Because the raw herb is not standardized, the amount of toxic alkaloids in any product can vary widely, making side effects unpredictable and potentially dangerous.

Madagascar Periwinkle: Reported Adverse Effects

Documented safety reports on Madagascar Periwinkle from the evidence-graded Natural Medicines (TRC Healthcare) database, shown word-for-word from the licensed record.

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. The vinca alkaloid constituents of Madagascar periwinkle have been reported to cause nausea, vomiting, alopecia, dizziness, nystagmus, vertigo, hearing impairment, leukopenia, thrombocytopenia, bleeding, hyperuricemia, neurotoxicity, and possibly death.

Exposure to the airborne pollen of Madagascar periwinkle can cause respiratory allergic reactions in sensitive individuals.

  1. Ellenhorn MJ, et al. Ellenhorn's Medical Toxicology: Diagnoses and Treatment of Human Poisoning. 2nd ed. Baltimore, MD: Williams & Wilkins, 1997.
  2. The Review of Natural Products by Facts and Comparisons. St. Louis, MO: Wolters Kluwer Co., 1999.
  3. McEvoy GK, ed. AHFS Drug Information. Bethesda, MD: American Society of Health-System Pharmacists, 1998.
  4. 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.
Reports by condition
Allergic rhinitis (hay fever) Immunologic

Exposure to the airborne pollen of Madagascar periwinkle can cause allergic respiratory reactions. In one population of adults with respiratory allergies, 29.8% tested positive to Madagascar periwinkle pollen during skin prick testing.

  1. 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.
Alopecia Dermatologic

Orally, Madagascar periwinkle can cause alopecia.

  1. Ellenhorn MJ, et al. Ellenhorn's Medical Toxicology: Diagnoses and Treatment of Human Poisoning. 2nd ed. Baltimore, MD: Williams & Wilkins, 1997.
Epilepsy Neurologic/CNS

Orally, Madagascar periwinkle can cause hallucinations and seizures. The vinca alkaloid constituents of Madagascar periwinkle have been reported to cause dizziness, vertigo, and neurotoxicity.

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

Orally, the vinca alkaloid constituents of Madagascar periwinkle have been reported to cause leukopenia, thrombocytopenia, bleeding, and hyperuricemia.

  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.
Nausea and vomiting Gastrointestinal

Orally, Madagascar periwinkle can cause gastrointestinal upset. The vinca alkaloid constituents of Madagascar periwinkle have been reported to cause nausea and vomiting.

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

Adverse-effects data: Natural Medicines, Therapeutic Research Center

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. They are not interchangeable with the herb in any form.

If you have seen this plant marketed as a supplement, talk to a pharmacist or doctor before considering it. In most cases, the safest choice is to avoid the raw herb entirely.

Pregnancy & Breastfeeding

Madagascar Periwinkle & Pregnancy

Likely Unsafe

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

  1. Brinker F. Herb Contraindications and Drug Interactions. 2nd ed. Sandy, OR: Eclectic Medical Publications, 1998.

Madagascar Periwinkle & Breastfeeding

Likely Unsafe

When used orally; avoid using.

  1. The Review of Natural Products by Facts and Comparisons. St. Louis, MO: Wolters Kluwer Co., 1999.
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

Pregnancy & lactation ratings: Natural Medicines, Therapeutic Research Center

References & further reading

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
Keep reading

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.

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

Brand directory

Brands that make products with Madagascar Periwinkle

4 brands in our database make a supplement containing Madagascar Periwinkle.

Product directory

Supplement products with Madagascar Periwinkle

8 products in our database contain Madagascar Periwinkle. Open any to see its full ingredient list and every drug interaction we check.

Pharmacist Counseling Corner

Madagascar Periwinkle: Common Questions

Does Madagascar Periwinkle interact with prescription medications?
Yes. We list 87 medications with a known interaction with Madagascar Periwinkle. Use the checker above to see how Madagascar Periwinkle interacts with a specific drug.
How are Madagascar Periwinkle interactions rated?
Each interaction is graded major, moderate, or minor based on how clinically significant it is and the strength of the evidence behind it. Major interactions are the most serious and are best avoided, or used only under close professional supervision.
Is it safe to take Madagascar Periwinkle with my medications?
It depends on the specific medication. Some combinations are fine, while others call for monitoring, timing changes, or should be avoided. Check your exact drug above and confirm with your pharmacist or doctor before starting, stopping, or changing anything.
Where does this Madagascar Periwinkle interaction information come from?
Our interaction data is built on the Natural Medicines database — an evidence-graded reference for vitamins, herbs, and supplements — and is reviewed by licensed HelloPharmacist pharmacists, who may add clinical context.
Is Madagascar Periwinkle the same as the cancer chemotherapy drug?
No. The plant is the natural source of compounds (vincristine and vinblastine) used to make chemotherapy drugs, but those drugs are purified, carefully dosed, and given by doctors. The raw plant is toxic and is not a treatment you can use at home.
Can I use Madagascar Periwinkle to treat diabetes or high blood pressure?
While it has been used this way in traditional medicine, there is not enough reliable evidence that it works, and the raw plant is toxic. Use proven, doctor-prescribed treatments instead and do not self-treat with this herb.
Is it safe to drink Madagascar Periwinkle tea?
No, this is not considered safe. The plant contains toxic alkaloids, and taking it as a tea or extract can cause poisoning. Avoid using the raw plant in any form.
Can I take it while pregnant or breastfeeding?
No. You should avoid Madagascar Periwinkle entirely during pregnancy and breastfeeding because its toxic compounds may harm a baby and there is no safe established dose.

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

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Products that contain Madagascar Periwinkle

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See all 8 products with Madagascar Periwinkle →
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