Drug & supplement interaction

Padang Cassia + Gefitinib

Gefitinib brand name: Iressa.

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

Gefitinib falls into 2 drug categories that Padang Cassia can interact with; the most serious is rated moderate. There is some concern that ingesting large amounts of Padang cassia might cause hepatotoxicity in some people.

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

Padang Cassia and Gefitinib

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

Why Are There 2 Interactions?

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

Moderate

HEPATOTOXIC DRUGS

1 of 2

Why this applies to Gefitinib

Gefitinib falls under HEPATOTOXIC DRUGS — the group Padang Cassia interacts with.

There is some concern that ingesting large amounts of Padang cassia might cause hepatotoxicity in some people. Padang cassia contains coumarin. Coumarin has caused hepatotoxicity in animal models. In otherwise healthy humans, very high doses of coumarin, from 50-7000 mg daily, can result in hepatotoxicity that resolves when coumarin use is discontinued. Lower amounts might also cause liver problems in sensitive people, such as those with liver disease or those taking potentially hepatotoxic agents.
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 concern with this pairing. Gefitinib (Iressa) can be tough on the liver on its own, and your care team usually checks your liver enzymes while you're on it. Concentrated cinnamon supplements like Padang cassia contain coumarin, a natural compound that has caused liver stress in animals and in people taking very high doses. Stacking a possible liver irritant on top of a cancer drug that already taxes the liver is the worry here.

Now, the honest truth: this is a theoretical caution based on how these substances behave, not proof it will harm you. Sprinkling cinnamon on your oatmeal is not the issue, it's the concentrated capsules that add up. Watch for yellowing skin or eyes, dark urine, or belly pain, and please check with your pharmacist or oncologist before taking cinnamon supplements.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Press release. Cinnamon capsules to reduce blood sugar are medicinal products! Efficacy has not been scientifically proven - some products contain high levels of coumarin. Federal Institute of Risk Assessment (BfM), Germany, November 11, 2006. Available a
  2. Felter SP, Vassallo JD, Carlton BD, Daston GP. A safety assessment of coumarin taking into account species-specificity of toxicokinetics. Food Chem Toxicol 2006;44:462-75. PubMed
  3. Choi, J., Lee, K. T., Ka, H., Jung, W. T., Jung, H. J., and Park, H. J. Constituents of the essential oil of the Cinnamomum cassia stem bark and the biological properties. Arch Pharm Res 2001;24(5):418-423.
  4. Wang R, Wang R, Yan B. Extraction of essential oils from five cinnamon leaves and identification of their volatile compound compositions. Innovative Food Science and Emerging Technologies 2009;10:289-92. DOI
  5. Wang YH, Avula B, Nanayakkara NP, et al. Cassia cinnamon as a source of coumarin in cinnamon-flavored food and food supplements in the United States. J Agric Food Chem 2013;61(18):4470-6. PubMed
  6. Woehrlin F, Fry H, Abraham K, Preiss-Weigert A. Quantification of flavoring constituents in cinnamon: high variation of coumarin in cassia bark from the German retail market and in authentic samples from Indonesia. J Agric Food Chem 2010;58(19):10568-75. PubMed
Moderate

CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES

2 of 2

Gefitinib also falls under CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES.

In vitro research shows that a methanol extract of Padang cassia inhibits cytochrome P450 3A4 (CYP3A4) activity. Theoretically, taking Padang cassia with CYP3A4 substrates might increase the effects and side effects of these substrates.
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 for gefitinib (Iressa). Your body relies on a liver enzyme called CYP3A4 to break this medicine down and clear it. Lab studies suggest that concentrated Padang cassia (a type of cassia cinnamon) may slow that enzyme down a bit. In theory, that could let more gefitinib hang around in your system, which can mean stronger effects and a higher chance of its usual side effects, like diarrhea, an acne-like skin rash, dry skin, mouth sores, or nausea.

I want to be honest about the strength of this: it's based only on test-tube research, not real people, so it's theoretical. The sprinkle of cinnamon in your oatmeal is very unlikely to matter. Concentrated cinnamon capsules are the real question. Since gefitinib is a cancer drug, please run any supplement past your oncology team or pharmacist first.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Subehan S, Kadota S, Tezuka Y. In vitro mechanism-based inactivation of cytochrome P450 3A4 by a new constituent of Cinnamomum burmani. Planta Med 2008;74(12):1474-80.

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

Padang Cassia Also Interacts With Other Medications

Padang Cassia has 933 moderate known drug interactions in our database — the Gefitinib one above is among them. If you take anything else, check it against the full list below.

Moderate 933 No known interaction 1,897 (incl. Gefitinib)
Taking anything else?

Check Another of Your Medications Against Padang Cassia

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

Everything else you take

See Every Supplement That Interacts With Gefitinib

This page covers Padang Cassia only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Gefitinib page lists 168 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Beer (major), Grapefruit (major), Siberian Cocklebur (major) and St. John's Wort (major).

By severity: 6 major · 124 moderate · 38 minor.

Open the Gefitinib interaction page

How much people look this up

Where Padang Cassia and Gefitinib 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 Padang Cassia
Top half

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

29 days ago today
Medication Gefitinib
Steady interest

#2,216 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 Padang Cassia

What is Padang Cassia?

  • Adding flavor to food
  • Digestive upset
  • Blood sugar support
  • Antimicrobial purposes
  • Antioxidant support

Padang Cassia is a type of cinnamon (Indonesian or Korintje cinnamon) grown mainly in Indonesia and used widely as a kitchen spice. As a supplement, evidence for health benefits like blood sugar control is limited and mixed, and like other cassia cinnamons it naturally contains coumarin, which can be harmful to the liver in large amounts. Use food amounts freely, but talk to a pharmacist or doctor before taking concentrated cinnamon supplements.

Read the full Padang Cassia monograph & all interactions
Medication

About Gefitinib

What Is Gefitinib Used For?

Brand name: Iressa

Gefitinib tablets — sold under the brand name Iressa — are used as a first-line treatment for metastatic non-small cell lung cancer (NSCLC). This treatment is only for patients whose tumors carry specific changes (mutations) in the EGFR gene: either an exon 19 deletion or an exon 21 (L858R) substitution mutation, confirmed by an FDA-approved test.

This medicine is not established as safe or effective for NSCLC patients with other types of EGFR mutations. Your doctor will use a genetic test on your tumor or blood to confirm whether gefitinib is right for you.

See full Gefitinib drug information
Keep checking

Other Drugs & Padang Cassia

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

0Major
933Moderate
0Minor
1,896No known interaction
933 Moderate 1,896 No interaction
Moderate

933 interactions

Showing 60 of 933 moderate interactions — see all 933 on the Padang Cassia page.

No interaction 1,896 drugs checked — show the list

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

Showing the 60 most looked-up of 1,896 medications checked with no known interaction — see the full Padang Cassia list.

See the full Padang Cassia interactions page
See every supplement checked against Gefitinib, 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
Padang Cassia monograph › Uses, safety, and every drug interaction in one place Gefitinib supplement interactions › Every supplement checked against Gefitinib, ranked by severity Gefitinib drug information › The full plain-English guide to this medication 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 Padang Cassia and Gefitinib Together: Common Questions

Can you take Padang Cassia with Gefitinib?
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 Padang Cassia and Gefitinib?
Gefitinib belongs to more than one drug category, and Padang Cassia 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 Padang Cassia and Gefitinib 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

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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.