Drug & supplement interaction

K2/spice + Entrectinib

Entrectinib brand name: Rozlytrek.

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

K2/spice has a moderate interaction with Entrectinib. Theoretically, K2/spice might have an additive effect with drugs that prolong the QT interval and increase the risk of ventricular arrhythmias.

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

K2/spice and Entrectinib

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

Moderate

QT INTERVAL-PROLONGING DRUGS

Why this applies to Entrectinib

Entrectinib falls under QT INTERVAL-PROLONGING DRUGS — the group K2/spice interacts with.

Theoretically, K2/spice might have an additive effect with drugs that prolong the QT interval and increase the risk of ventricular arrhythmias.
There have been numerous cases of increased QT and corrected QT intervals in patients using K2/spice.
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

First things first: K2/Spice isn't an herb or a safe natural product. It's plant material sprayed with man-made cannabinoid chemicals that vary wildly from batch to batch, and it has been tied to seizures, psychosis, dangerous heart rhythms, and deaths. I wouldn't use it under any circumstances, and that goes double while you're on cancer treatment.

Here's the specific concern with Entrectinib (Rozlytrek): this medication can stretch out the heart's electrical cycle, something called QT prolongation. K2/Spice has been linked in real-world reports to the same thing. Stacking the two could add up and raise the risk of a serious, irregular heartbeat. This is based on case reports rather than strong studies, so it's more theoretical, but the stakes are high enough that it isn't worth the gamble. Please loop in your oncologist or pharmacist.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Ahmed T, Khan A, See VY, Robinson S. Cardiac arrest associated with synthetic cannabinoid use and acquired prolonged QTc interval: A case report and review of literature. HeartRhythm Case Rep. 2020;6(5):283-286. PubMed
  2. Yildiz SS, Sutasir MN, Sigirci S, et al. Acute effects of synthetic cannabinoids on ventricular repolarization parameters. Turk Kardiyol Dern Ars. 2019;47(5):384-390.

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

K2/spice Also Interacts With Other Medications

K2/spice has 207 moderate known drug interactions in our database — the Entrectinib one above is one of them. If you take anything else, check it against the full list below.

Moderate 207 No known interaction 2,623 (incl. Entrectinib)
Taking anything else?

Check Another of Your Medications Against K2/spice

Covers the 2,830 medications we’ve checked against K2/spice. Pick one to open its full report.

Everything else you take

See Every Supplement That Interacts With Entrectinib

This page covers K2/spice only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Entrectinib page lists 175 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), American Hellebore (major), Arsenic (major), Beer (major) and Cesium (major).

By severity: 11 major · 127 moderate · 37 minor.

From our pharmacist’s overview on the Entrectinib page

“Grapefruit tops my worry list for anyone taking entrectinib (Rozlytrek), a targeted cancer therapy cleared by the liver enzyme CYP3A4. 121 of the 175 supplement ingredients on this page can shift how that enzyme handles the drug.”

Reviewed by 2 · Jul 18, 2026

Open the Entrectinib interaction page

How much people look this up

Where K2/spice and Entrectinib 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 K2/spice
Steady interest

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

29 days ago today
Medication Entrectinib
Top half

#1,026 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 K2/spice

What is K2/spice?

  • Recreational drug ('legal high')
  • Marijuana substitute
  • Mood or perception changes
  • Sometimes used to avoid drug testing

K2/Spice is NOT a herbal supplement — it is plant material sprayed with man-made synthetic cannabinoid chemicals. It is dangerous, unpredictable, and has caused seizures, heart problems, psychosis, and deaths, so it should not be used.

Read the full K2/spice monograph & all interactions
Medication

About Entrectinib

What Is Entrectinib Used For?

Brand name: Rozlytrek

Rozlytrek (entrectinib) is used to treat adult patients with ROS1-positive metastatic non-small cell lung cancer (NSCLC), as confirmed by an FDA-approved test. It is also approved for adult and pediatric patients older than 1 month of age who have solid tumors — any cancer type — that carry an NTRK gene fusion detected by an FDA-approved test, provided the tumor has no known acquired resistance mutation, is metastatic or cannot be surgically removed without severe harm, and has progressed after prior treatment or has no satisfactory alternative therapy.

The NTRK gene fusion approval in solid tumors was granted under accelerated approval, meaning it is based on tumor response rates. Continued approval may depend on results from confirmatory clinical trials.

See full Entrectinib drug information
Keep checking

Other Drugs & K2/spice

Browse every other medication we’ve checked against K2/spice — both the ones with a known interaction and the ones without. Select any drug for the full detail.

0Major
207Moderate
0Minor
2,622No known interaction
207 Moderate 2,622 No interaction
Moderate

207 interactions

Showing 60 of 207 moderate interactions — see all 207 on the K2/spice page.

No interaction 2,622 drugs checked — show the list

We also checked K2/spice against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 2,622 medications checked with no known interaction — see the full K2/spice list.

See the full K2/spice interactions page
See every supplement checked against Entrectinib, 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
K2/spice monograph › Uses, safety, and every drug interaction in one place Entrectinib supplement interactions › Every supplement checked against Entrectinib, ranked by severity Entrectinib 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 K2/spice and Entrectinib Together: Common Questions

Can you take K2/spice with Entrectinib?
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 K2/spice and Entrectinib 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 Entrectinib and K2/spice?

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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.