Laura Pole, RN, MSN, OCNS, BCCT Senior Researcher

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Nancy Hepp, MS, BCCT Project Manager

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Last updated August 12, 2021.

Cimetidine is an antacid and antihistamine medication, in a class of medications called H2 antagonists or H2 blockers. It is used mainly to treat ulcers of the stomach and intestines and prevent their return. 

Other H2 blockers include famotidine, nizatidine and ranitidine. Most of the research regarding effects in cancer involves cimetidine.

Treating the Cancer

Working against cancer growth or spread, improving survival, or working with other treatments or therapies to improve their anticancer action.

Cimetidine has shown the following effects in preventing tumor cell growth and metastasis:1

  • Prevents cancer cell adhesion
  • Prevents the development of blood vessels to supply tumors (anti-angiogenesis)
  • Reduces cancer cell growth and spread (anti-proliferation)
  • Induces cell death (apoptosis)
  • Inhibits immunosuppression that typically follows surgery
  • Enhances other biologically active treatments

Also known by these brand names

CVS Health Heartburn Relief
Equaline Acid Reducer
Leader Heartburn Relief
Tagamet HB
Tagamet Pro

Preclinical and clinical reports show that cimetidine may be a promising drug to repurpose for cancer treatment. It regulates the immune system, and its most promising use may be near the time of surgical removal (resection) of solid tumors in combination with other standard treatments.2

Key Points

  • Cimetidine is an over-the-counter drug approved by the FDA to inhibit the secretion of stomach acid. Its use in cancer is considered off-label.
  • Even though the H2 blocker drugs don’t require a prescription, consulting your oncology team about interactions with other treatments and therapies is very important. Also check that this therapy is safe for use with any other medical conditions you may have.
  • Cimetidine reduces cancer growth and spread; it also enhances anticancer immunity and the effectiveness of conventional cancer treatments in some cancers. It may also reduce treatment side effects.
  • Some of the benefits are seen when cimetidine is used in combination with other therapies.

Clinical Evidence

Unspecified or Multiple Cancers

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Brain Cancer (Glioblastoma)

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Breast Cancer

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Colorectal Cancer

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Kidney Cancer (Renal Cell Carcinoma)

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Lung Cancer

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Stomach Cancer or Gastrointestinal Cancers

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Lab and Animal Evidence

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Managing Side Effects and Promoting Wellness

Managing or relieving side effects or symptoms, reducing treatment toxicity, supporting quality of life or promoting general well-being

Clinical Evidence

  • Reduced suppression of immune function that typically follows surgical removal (resection),25 including a more rapid return to pre-operative immune function after surgery26  
  • Reduced cisplatin's kidney toxicity (nephrotoxicity) without compromising the success of tumor therapy27

Lab and Animal Evidence

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Optimizing Your Terrain

Creating an environment within your body that does not support cancer development, growth or spread

  • Increased numbers of anticancer immune cells30
  • Regulated or normalized anticancer functions of the immune system31
  • Increased production of antitumor signalling proteins (cytokines)32


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


Cimetidine overall has low toxicity; however, several cautions and side effects are noted. Consult your physician and your pharmacist prior to taking this drug. 

Cimetidine can interfere with vitamin D metabolism, preventing an expected rise in serum levels and the benefits from that.33

Common Side Effects/Adverse Events

Reported side effects:34

  • Elevated estrogen levels; use cautiously in those with breast and gynecologic cancers;35 use can produce galactorrhea (a milky nipple discharge) in women and gynecomastia (enlargement or swelling of breast tissue) in men
  • Male sexual dysfunction
  • Increased potential for bone marrow suppression (myelosuppression) when used together with drugs capable of causing bone marrow suppression

Interactions with Other Treatments

From a review in 2014:36

  • Hydroxychloroquine: cimetidine may interact with the antimalarial medication hydroxychloroquine (another drug used off-label for some types of cancer). 
  • Methadone and opioids: cimetidine affects the metabolism of methadone, sometimes resulting in higher blood levels and a higher incidence of side effects. Cimetidine is also known to increase the effects of several opioids and can lead to extreme plasma levels of these drugs and a fatal overdose. 
  • Psychoactive medications: cimetidine can interact with a number of different psychoactive medications, including tricyclic antidepressants and selective serotonin reuptake inhibitors, causing increased blood levels of these drugs and subsequent toxicity.


BCCT does not recommend therapies or doses, but only provides information for patients and providers to consider as part of a complete treatment plan. Patients should discuss therapies with their physicians, as contraindications, interactions and side effects must be evaluated. 

Integrative Programs, Protocols and Medical Systems

For more information about protocols, see our Protocols page.

  • Used in these programs and protocols:


From Clinical Pearls, Cancer Strategies Journal (Summer 2013. p.7) edited by BCCT advisor Dwight McKee, MD: "Given its low toxicity and low cost, cimetidine can probably be administered to patients with colorectal cancer and possibly other adenocarcinomas that express the Sialyl Lewis antigens to minimize metastases and recurrence and enhance survival.”

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