Drug & supplement interaction

Quassia + Simvastatin, Sitagliptin

Simvastatin, Sitagliptin brand name: Juvisync.

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

Quassia has a moderate interaction with Simvastatin, Sitagliptin. In animals, quassia extract reduced levels of fasting glucose.

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

Quassia and Simvastatin, Sitagliptin

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

Moderate

ANTIDIABETES DRUGS

Why this applies to Simvastatin, Sitagliptin

Simvastatin, Sitagliptin falls under ANTIDIABETES DRUGS — the group Quassia interacts with.

In animals, quassia extract reduced levels of fasting glucose. Theoretically, quassia might have additive effects when used with antidiabetes drugs. This might increase the risk of hypoglycemia in some patients. Monitor blood glucose levels closely.
Some antidiabetes drugs include glimepiride (Amaryl), glyburide (DiaBeta, Glynase PresTab, Micronase), insulin, metformin (Glucophage), pioglitazone (Actos), rosiglitazone (Avandia), and others.
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

Juvisync is a combo pill: simvastatin (a cholesterol medicine) plus sitagliptin, which is the part that lowers blood sugar in type 2 diabetes. The concern here is with the sitagliptin half. In animal studies, quassia seemed to nudge fasting blood sugar down a bit. So the worry is simple math: if quassia also lowers sugar, stacking it on top of your diabetes medicine could push your levels too low.

Keep in mind this is theoretical and only based on lab and animal work, not people, so it may not amount to much. Still, watch for signs of low blood sugar like shakiness, sweating, dizziness, or feeling foggy. The statin side isn't really affected here. If you'd like to try quassia, check your sugars closely and chat with your pharmacist or doctor first.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Husain GM, Singh PN, Singh RK, Kumar V. Antidiabetic activity of standardized extract of Quassia amara in nicotinamide-streptozotocin-induced diabetic rats. Phytother Res. 2011;25(12):1806-12.

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

Quassia Also Interacts With Other Medications

Quassia has 161 moderate, 36 minor known drug interactions in our database — the Simvastatin, Sitagliptin one above is one of them. If you take anything else, check it against the full list below.

Moderate 161 Minor 36 No known interaction 2,633 (incl. Simvastatin, Sitagliptin)
Taking anything else?

Check Another of Your Medications Against Quassia

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

Everything else you take

See Every Supplement That Interacts With Simvastatin, Sitagliptin

This page covers Quassia only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Simvastatin, Sitagliptin page lists 362 supplements it has a documented interaction with, worst first, each one explained.

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

By severity: 8 major · 304 moderate · 50 minor.

From our pharmacist’s overview on the Simvastatin, Sitagliptin page

“Juvisync pairs simvastatin for cholesterol with sitagliptin for type 2 diabetes, and that combination carries 362 supplement interactions on file, eight rated major, so read this page with real care rather than a quick skim. Grapefruit stands out as the everyday hazard; it blocks the enzyme that clears simvastatin, raising statin level…”

Reviewed by 2 · Jul 18, 2026

Open the Simvastatin, Sitagliptin interaction page

One more smart check

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

We hold 172 real supplement products containing Quassia, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Quassia. Your product may carry other ingredients that interact with Simvastatin, Sitagliptin too, on top of Quassia — 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 Quassia and Simvastatin, Sitagliptin 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 Quassia
Top half

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

29 days ago today
Medication Simvastatin, Sitagliptin
Top half

#886 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 Quassia

What is Quassia?

  • Loss of appetite
  • Digestive upset
  • Head lice (topical)
  • Intestinal worms/parasites
  • Bitter tonic

Quassia is a tropical wood known for its very bitter taste, traditionally used as a digestive bitter and as a folk remedy for parasites and head lice. Human evidence for these uses is limited, and high doses may irritate the stomach, so it should be used cautiously and avoided in pregnancy.

Read the full Quassia monograph & all interactions
Keep checking

Other Drugs & Quassia

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

0Major
161Moderate
36Minor
2,632No known interaction
161 Moderate 36 Minor 2,632 No interaction
Moderate

161 interactions

Showing 60 of 161 moderate interactions — see all 161 on the Quassia page.

Minor

36 interactions

No interaction 2,632 drugs checked — show the list

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

Showing the 60 most looked-up of 2,632 medications checked with no known interaction — see the full Quassia list.

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

Can you take Quassia with Simvastatin, Sitagliptin?
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 Quassia and Simvastatin, Sitagliptin 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.