Cimetidine and Other H2 Blockers for Cancer

Cimetidine and Other H2 Blockers for Cancer: What They Are and How They May Help

Authors

Nancy Hepp, MS

past Lead Researcher

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Ms. Hepp is a researcher and communicator who has been writing and editing educational content on varied health topics for more than 20 years. She serves as lead researcher and writer for CancerChoices and also served as the first program manager. Her graduate work in research and cognitive psychology, her master’s degree in instructional design, and her certificate in web design have all guided her in writing and presenting information for a wide variety of audiences and uses. Nancy’s service as faculty development coordinator in the Department of Family Medicine at Wright State University also provided experience in medical research, plus insights into medical education and medical care from the professional’s perspective.

Nancy Hepp, MS past Lead Researcher

Laura Pole, MSN, RN, OCNS

Senior Clinical Consultant

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Laura Pole is senior clinical consultant for CancerChoices. Laura is an oncology clinical nurse specialist who has been providing integrative oncology clinical care, navigation, consultation, and education services for over 40 years. She is the co-creator and co-coordinator of the Integrative Oncology Navigation Training at Smith Center for Healing and the Arts in Washington, DC. Laura also manages the “Media Watch Cancer News That You Can Use” listserv for Smith Center/Commonweal. In her role as a palliative care educator and consultant, Laura has served as statewide Respecting Choices Faculty for the Virginia POST (Physician Orders for Scope of Treatment) Collaborative as well as provided statewide professional education on palliative and end-of-life care for the Virginia Association for Hospices and Palliative Care.

For CancerChoices, Laura curates content and research, networks with clinical and organizational partners, brings awareness and education of integrative oncology at professional and patient conferences and programs, and translates research into information relevant to the patient experience as well as clinical practice.

Laura sees her work with CancerChoices as a perfect alignment of all her passions, knowledge and skills in integrative oncology care. She is honored to serve you.

Laura Pole, MSN, RN, OCNS Senior Clinical Consultant

Clinical reviewer

Susan Yaguda, MSN, RN

Manager at Atrium Health’s Levine Cancer Institute and CancerChoices Clinical Consultant

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Susan Yaguda, MSN, RN, has been a nurse for nearly 40 years, working in a variety of healthcare settings. She currently works in Charlotte, North Carolina, at Atrium Health’s Levine Cancer Institute as the manager for Integrative Oncology and Cancer Survivorship. She works with a multidisciplinary team to deliver holistic, evidence-based support and education for patients and care partners at any point along the trajectory of cancer care. She completed the Integrative Oncology Scholars Program through the University of Michigan in 2020, is certified as an Integrative Health Coach through Duke Integrative Medicine and has a post-graduate certificate in Nursing Education from the University of North Carolina, Charlotte. Susan also was awarded the Planetree International Scholar’s Award in 2018 and was recognized by the Daisy Foundation for Nurse Leadership in 2021. Susan has a particular interest in empowering patients and care partners with knowledge to help drive informed decision making and educating nurses on the benefits of integrative care for patients and self-care. She has presented nationally and internationally on integrative oncology and nursing education.

She and her husband, Mark, have two adult children and a very spoiled foxhound. She enjoys hiking, knitting, cooking, and pickleball.

“As a frequent consumer of Beyond Conventional Cancer Therapies, and now CancerChoices, for both professional education and patient support, it is an honor to have the opportunity to engage with the dedicated team at CancerChoices to serve those impacted by this disease.”  

 

Susan Yaguda, MSN, RN Manager at Atrium Health’s Levine Cancer Institute and CancerChoices Clinical Consultant

Last update: September 11, 2026

Cimetidine and other H2 blockers for cancer: what you need to know

• Cimetidine and other H2 blockers are used to treat gastrointestinal ulcers and/or reduce stomach acid; they are available as over-the-counter medications and as prescription drugs.
• The use of cimetidine and other H2 blockers for treating cancer is considered off-label.
• Some studies show better survival among people with colorectal cancer treated with cimetidine. Evidence of benefit for other cancers is preliminary and some studies show no effect.
• Significant safety concerns; it’s essential to use cimetidine and other H2 blockers only under medical supervision.
• This is not a standalone treatment for cancer; it is a complementary therapy used alongside standard medical care to support treatment and/or well-being.

What are cimetidine and other H2 blockers?

Cimetidine and other H2 blockers are used to treat gastrointestinal ulcers and/or reduce stomach acid. They are available both as over-the-counter medications for heartburn and stomach acid and as prescription drugs. Their use in treating cancer is considered off-label. 

Some studies show better survival among people with colorectal cancer treated with cimetidine. Studies on other cancers are preliminary and while a few suggest possible benefits for survival or tumor response, others found no effect. 

Safety

• Supervision by a medical professional is essential.
• Cimetidine or other H2 blockers may affect the efficacy of some cancer treatments.
• Use of ranitidine—but not other H2 blockers—is linked to higher risk of one type of breast cancer.
• H2 blockers should be used with caution during chemotherapy and among people with estrogen-sensitive cancers, including some breast cancers and gynecologic cancers.
• Known interactions, consult with your healthcare provider before adding to your regimen.

See full safety details, side effects & drug interactions →

How cimetidine and other H2 blockers may help people with cancer

Strength of evidence rating

We rate the strength of the evidence with 0=no evidence, 1=weak evidence, 2=modest evidence, and 3=good evidence. Read more about our method in detail here ›

Optimizing your body terrain

In several small studies, people with cancer treated with cimetidine showed higher markers of immune activation.¹³Li B, Cao F et al. Perioperative cimetidine administration improves systematic immune response and tumor infiltrating lymphocytes in patients with colorectal cancer. Hepatogastroenterology 2013;60:244–247; Lin CY, Bai DJ, Yuan HY, et al. Perioperative cimetidine administration promotes peripheral blood lymphocytes and tumor infiltrating lymphocytes in patients with gastrointestinal cancer: results of a randomized controlled clinical trial. World Journal of Gastroenterology. 2004;10(1):136–142; Adams WJ, Morris DL. Pilot study—cimetidine enhances lymphocyte infiltration of human colorectal carcinoma: results of a small randomized control trial. Cancer. 1997 Jul 1;80(1):15-21; Kurosu Y, Tanaka N, Furusho Y, Morita K. Cimetidine-mediated augmentation of lymphocyte responses to phytohemagglutinin in gastric cancer patients. Japanese Journal of Clinical Oncology. 1989 Mar;19(1):56-61; Flodgren P, Sjögren HO. Influence in vitro on NK and K cell activities by cimetidine and indomethacin with and without simultaneous exposure to interferon. Cancer Immunology, Immunotherapy. 1985;19(1):28-34. In one small study, people with B cell chronic lymphocytic leukemia treated with ranitidine (an H2 blocker) and vaccinated for Haemophilus influenzae type-B showed better vaccination response.¹⁴Jurlander J, de Nully Brown P et al. Improved vaccination response during ranitidine treatment, and increased plasma histamine concentrations, in patients with B cell chronic lymphocytic leukemia. Leukemia. 1995 Nov;9(11):1902-9.

Increased immune system activation is not always beneficial, so your oncology team needs to determine whether immune activation would be favorable in your situation.

Reducing cancer risk or recurrence

The data on H2 blockers reducing the risk of developing a new cancer, or a cancer recurrence, are mixed and there is no strong conclusion on if they have an impact on risk or recurrence. 

In a study of people with diabetes, those using H2 blockers for over one year showed moderately lower risk of lung cancer (squamous cell carcinoma and adenocarcinoma, with stronger effects for adenocarcinoma).¹⁵Hsu CL, Chang CH et al. Histamine-2 receptor antagonists and risk of lung cancer in diabetic patients—an exploratory analysis. Pharmacoepidemiology and Drug Safety. 2013 Jun;22(6):632-40.

Studies of people using H2 blockers around the time of surgery for colorectal cancer found mixed results: one study found no evidence of an effect on recurrence,¹⁶Jameson MB, Michael Arendse et al. Final analysis of a randomized placebo-controlled double-blind phase II trial of perioperative cimetidine (CIM) in early colorectal cancer (CRC). Journal of Clinical Oncology. 2018;36(15_suppl):e15678-e15678. while another found substantially longer time to recurrence and better survival.¹⁷Ali AH, Hale L et al. The effect of perioperative cimetidine administration on time to colorectal cancer recurrence. American Journal of Therapeutics. 2018 Jul/Aug;25(4):e405-e411. In an analysis of 3 studies of people using H2 blockers after removal of colorectal adenomas (benign tumors that may become cancerous), no effect was seen on risk of recurrence.¹⁸Robertson DJ, Burke CA et al. Histamine receptor antagonists and incident colorectal adenomas. Alimentary Pharmacology & Therapeutics. 2005 Jul 15;22(2):123-8. 

See the full evidence summary ›

Affordability and access

Is a prescription required?

• Cimetidine is available both by prescription and as an over-the-counter drug.

Other names and brands

Other names for H2 blockers:

• H2-antihistaminics
• Type 2 histamine receptor antagonists
• Histamine-2 receptor blockers (H2RBs)

Individual H2 blockers:

• Cimetidine
• Famotidine
• Ranitidine

Where to find it

• Drug stores
• Online supplement distributors

Affordability

• Moderate cost (between $40 US and $160 US/month)
• Generally covered by insurance when prescribed by a doctor

Find an integrative provider ›

FAQs

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• Sourcing Quality Herbs & Supplements ›
• Supplement and Therapies Database ›

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