Drug & supplement interaction

Delta-9-tetrahydrocannabinol (thc) + Cyclophosphamide

Cyclophosphamide brand names: Cytoxan, Neosar.

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

Delta-9-tetrahydrocannabinol (thc) has a minor interaction with Cyclophosphamide. Theoretically, THC may increase the levels and clinical effects of CYP3A4 substrates.

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

Delta-9-tetrahydrocannabinol (thc) and Cyclophosphamide

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

Minor

CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES

Why this applies to Cyclophosphamide

Cyclophosphamide falls under CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES — the group Delta-9-tetrahydrocannabinol (thc) interacts with.

Theoretically, THC may increase the levels and clinical effects of CYP3A4 substrates.
In vitro research shows that cannabis containing THC might modestly inhibit the activity of CYP3A4 enzymes, which might decrease the metabolism of CYP3A4 substrates. It is unclear if this effect is due to THC, other constituents, or the combination. In vitro research also shows that cannabis extracts containing THC modestly inhibit the CYP3A4 metabolism of testosterone; extracts providing the specific cannabinoids cannabidiol (CBD) or cannabigerol (CBG) alone had stronger inhibitory effects than extracts containing both THC and CBD. Conversely, a crossover clinical study in healthy adults shows that oral THC does not inhibit CYP3A4.
Severity Minor Likelihood Unlikely Evidence D

Interaction has been demonstrated in animal or in lab research but has been shown not to occur in humans..

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's something worth knowing about combining THC with cyclophosphamide. Cyclophosphamide is actually a prodrug, meaning it has to be turned on by liver enzymes (including CYP3A4) before it can fight cancer. The lab-based concern is that THC might slightly block CYP3A4. In theory, slowing that enzyme could shift how much active drug your body makes, which gets complicated with a powerful chemo medicine like this one.

I want to be honest about the evidence here: this is rated as a minor, unlikely interaction based only on test-tube studies, and one human study actually showed oral THC did not block CYP3A4. So it's more theoretical than proven. Still, because cyclophosphamide is serious chemo, please loop in your oncology team or pharmacist before using any THC product, including dronabinol for nausea.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Pellinen, P., Honkakoski, P., Stenback, F., Niemitz, M., Alhava, E., Pelkonen, O., Lang, M. A., and Pasanen, M. Cocaine N-demethylation and the metabolism-related hepatotoxicity can be prevented by cytochrome P450 3A inhibitors. Eur.J Pharmacol 1-3-1994;2 PubMed
  2. Treyer A, Reinhardt JK, Eigenmann DE, Oufir M, Hamburger M. Phytochemical comparison of medicinal cannabis extracts and study of their CYP-mediated interactions with coumarinic oral anticoagulants. Med Cannabis Cannabinoids. 2023;6(1):21-31. PubMed
  3. Bansal S, Zamarripa CA, Spindle TR, et al. Evaluation of Cytochrome P450-Mediated Cannabinoid-Drug Interactions in Healthy Adult Participants. Clin Pharmacol Ther 2023.

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

Delta-9-tetrahydrocannabinol (thc) Also Interacts With Other Medications

Delta-9-tetrahydrocannabinol (thc) has 762 moderate, 335 minor known drug interactions in our database — the Cyclophosphamide one above is one of them. If you take anything else, check it against the full list below.

Moderate 762 Minor 335 No known interaction 1,733 (incl. Cyclophosphamide)
Taking anything else?

Check Another of Your Medications Against Delta-9-tetrahydrocannabinol (thc)

Covers the 2,830 medications we’ve checked against Delta-9-tetrahydrocannabinol (thc). Pick one to open its full report.

Everything else you take

See Every Supplement That Interacts With Cyclophosphamide

This page covers Delta-9-tetrahydrocannabinol (thc) only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Cyclophosphamide page lists 220 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 · 176 moderate · 38 minor.

Open the Cyclophosphamide interaction page

How much people look this up

Where Delta-9-tetrahydrocannabinol (thc) and Cyclophosphamide 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 Delta-9-tetrahydrocannabinol (thc)
Top half

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

29 days ago today
Medication Cyclophosphamide
Steady interest

#1,707 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 Delta-9-tetrahydrocannabinol (thc)

What is Delta-9-tetrahydrocannabinol (thc)?

Delta-9-tetrahydrocannabinol (thc)
  • Chronic or nerve pain
  • Nausea and vomiting from chemotherapy
  • Appetite loss and weight loss
  • Muscle spasticity
  • Sleep problems
  • Anxiety and stress

THC is the main mind-altering compound in cannabis and is best known for causing a 'high.' A prescription form (dronabinol) is approved for chemotherapy-related nausea and appetite loss, but for most other uses the evidence is mixed or limited, and THC can impair thinking and driving. It should be avoided in pregnancy and breastfeeding and used only with medical guidance.

Read the full Delta-9-tetrahydrocannabinol (thc) monograph & all interactions
Medication

About Cyclophosphamide

What Is Cyclophosphamide Used For?

Brand names: Cytoxan, Neosar

Cyclophosphamide is used to treat many types of cancer in adults and children, including malignant lymphomas (such as Hodgkin's disease and Burkitt's lymphoma), multiple myeloma, several forms of leukemia, breast cancer, ovarian cancer, neuroblastoma, retinoblastoma, and advanced mycosis fungoides (a type of skin lymphoma). It is often given alongside other chemotherapy drugs rather than on its own.

Oral and injectable powder formulations (but not the Cyclophosphamide Injection solution concentrate) are also approved for minimal change nephrotic syndrome — a kidney condition — in children who have not responded well to, or cannot tolerate, steroid therapy. The injectable solution concentrate is approved for adult patients only due to its alcohol content, and is not approved for use in children.

See full Cyclophosphamide drug information
Keep checking

Other Drugs & Delta-9-tetrahydrocannabinol (thc)

Browse every other medication we’ve checked against Delta-9-tetrahydrocannabinol (thc) — both the ones with a known interaction and the ones without. Select any drug for the full detail.

0Major
762Moderate
335Minor
1,732No known interaction
762 Moderate 335 Minor 1,732 No interaction
Moderate

762 interactions

Showing 60 of 762 moderate interactions — see all 762 on the Delta-9-tetrahydrocannabinol (thc) page.

Minor

335 interactions

Showing 60 of 335 minor interactions — see all 335 on the Delta-9-tetrahydrocannabinol (thc) page.

No interaction 1,732 drugs checked — show the list

We also checked Delta-9-tetrahydrocannabinol (thc) against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 1,732 medications checked with no known interaction — see the full Delta-9-tetrahydrocannabinol (thc) list.

See the full Delta-9-tetrahydrocannabinol (thc) interactions page
See every supplement checked against Cyclophosphamide, 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
Delta-9-tetrahydrocannabinol (thc) monograph › Uses, safety, and every drug interaction in one place Cyclophosphamide supplement interactions › Every supplement checked against Cyclophosphamide, ranked by severity Cyclophosphamide 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 Delta-9-tetrahydrocannabinol (thc) and Cyclophosphamide Together: Common Questions

Can you take Delta-9-tetrahydrocannabinol (thc) with Cyclophosphamide?
There is only a minor interaction, which is usually not serious. Read the full details on this page and confirm with your pharmacist before combining them.
How serious is the Delta-9-tetrahydrocannabinol (thc) and Cyclophosphamide interaction?
We rate it Minor. This interaction is generally not clinically significant, but it remains worth noting and discussing with your pharmacist.

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

Still Have a Question About Cyclophosphamide and Delta-9-tetrahydrocannabinol (thc)?

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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.