This page records what is documented between something in this register and a
class of cancer treatment. It is not a check of your medicines and it cannot be
one: the register cannot see your prescription, your doses or your history, and
the list below is short because the evidence is short, not because the rest has
been cleared.
Interaction checking at the level of individual drugs is a pharmacy system's
job. This page exists to get the question to a pharmacist, who has your full
list and whose job this is.
Antibiotics around the start of checkpoint immunotherapy
Recorded as documented, against Checkpoint immunotherapy.
Antibiotic use around the start of checkpoint immunotherapy has been associated with poorer response. This one runs between two prescribed treatments rather than between a supplement and a drug, so it is a question for the team prescribing both.
If I need antibiotics around the time my immunotherapy starts, is the timing something you would weigh?
Routy B, Le Chatelier E, Derosa L, et al. Gut microbiome influences efficacy of PD-1-based immunotherapy against epithelial tumors. Science 2018;359:91-97. doi:10.1126/science.aan3706
Cannabis alongside checkpoint immunotherapy
Recorded as documented, against Checkpoint immunotherapy.
A retrospective study reported a lower response rate to one immunotherapy drug among people also using cannabis. The finding is contested and the critique of it is on the cannabis page. It is recorded because it points the opposite way to what most readers expect.
Is there any reason my immunotherapy and cannabis should not be running at the same time?
Taha T, Meiri D, Talhamy S, Wollner M, Peer A, Bar-Sela G. Cannabis impacts tumor response rate to nivolumab in patients with advanced malignancies. The Oncologist 2019;24(4):549-554. doi:10.1634/theoncologist.2018-0383 · Piper BJ, Tian M, Saini P, et al. Immunotherapy and cannabis: a harmful drug interaction or reefer madness? Cancers 2024;16:1245.
Recorded as documented, against Checkpoint immunotherapy.
Among people receiving immunotherapy for melanoma, those taking a probiotic supplement had a lower response rate. The signal is observational and it points the opposite way to what most people expect from a probiotic.
Does taking a probiotic supplement matter while I am on immunotherapy?
Spencer CN, McQuade JL, Gopalakrishnan V, et al, and 86 further authors. Dietary fiber and probiotics influence the gut microbiome and melanoma immunotherapy response. Science 2021;374(6575):1632-1640. doi:10.1126/science.aaz7015
Fenbendazole
Recorded as documented, with no particular treatment named by the source, so it is shown against all of them.
Fenbendazole is processed by the liver enzymes that also clear many cancer drugs, and a professional body states that its use may alter how established cancer treatments behave in the body. The route is named and the size of the effect has never been measured in a person, because no human pharmacokinetic study of fenbendazole exists. The source names no particular treatment, so this is shown against all of them.
Does fenbendazole going through the same liver enzymes as some cancer drugs matter for what I am on?
ASCO Clinical Notice, May 2026, recommending against ivermectin and fenbendazole for cancer treatment outside of clinical trials. Published by the American Society of Clinical Oncology. source
Ivermectin
Recorded as documented, with no particular treatment named by the source, so it is shown against all of them.
Ivermectin is processed by the liver enzymes that also clear many cancer drugs, and a professional body states that its use may alter how established cancer therapies behave in the body. The mechanism is named; the size of the effect has not been measured in anyone taking it for cancer. The source names no particular treatment, so this is shown against all of them.
Does ivermectin going through the same liver enzymes as some cancer drugs matter for what I am on?
ASCO Clinical Notice, May 2026, recommending against ivermectin and fenbendazole for cancer treatment outside of clinical trials. Published by the American Society of Clinical Oncology. source
Methylene blue
Recorded as documented, with no particular treatment named by the source, so it is shown against all of them.
Methylene blue is a potent inhibitor of monoamine oxidase A, and product labelling records serotonin syndrome in people also taking serotonergic medicines, a class widely prescribed to people with cancer. It also inhibits liver enzymes that clear a number of other drugs, and it is contraindicated in glucose-6-phosphate dehydrogenase deficiency. This register does not check interactions at the level of individual drugs and will not; this entry exists to put the question to a pharmacist, who can.
Can you check methylene blue, which is recorded as interacting with medicines that act on serotonin and with some liver enzymes, against everything on my list?
Product labelling for methylene blue class products, and a paper titled Methylene blue and serotonin toxicity: inhibition of monoamine oxidase A confirms a theoretical prediction. doi:10.1038/sj.bjp.0707430 · Product information for methylene blue recording contraindication in glucose-6-phosphate dehydrogenase deficiency and a list of drugs that may accumulate through inhibition of cytochrome P450 isozymes.
Apricot kernels or laetrile, with vitamin C
Recorded as documented, between two compounds rather than against a cancer treatment.
The Cochrane review of laetrile records that the risk of cyanide poisoning could increase alongside vitamin C, and in people who are vegetarian with low vitamin B12. Vitamin C is among the most commonly taken supplements in this readership, which is why this is recorded on both pages. It runs between two compounds rather than against a cancer treatment, so it never appears in the treatment-class list.
Can you look at what I have read about laetrile and vitamin C together raising the risk of cyanide poisoning?
Milazzo S, Horneber M. Laetrile treatment for cancer. Cochrane Database of Systematic Reviews 2015;4:CD005476. doi:10.1002/14651858.CD005476.pub4
Taking this to a pharmacist
Add the questions you want asked, then open
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is headed as a request for a review, not as a finding, because a finding is not
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