Written by: Dr. Adam McLeod, ND, BSc(Hons)
Many cancer patients undergoing chemotherapy have constant disturbances in their gastrointestinal tract. Heartburn is very common in these patients and it is frequently treated with a class of drugs called proton pump inhibitors (PPI’s). Some common PPI’s are Pariet, Losec, Nexium and Tecta. There is no question that these drugs are effective at controlling heart burn symptoms. These drugs dramatically suppress the stomach’s ability to produce acid. When patients are on these drugs long term it can be difficult to discontinue them because heart burn symptoms reappear whenever they miss a dose. In the context of cancer there are other options that can be considered before using PPI’s.
There is a class of drugs called H2-receptor antagonists and these drugs are also very effective at reducing stomach acid production. The reduction in stomach acid tends to be short term and patients do not become as dependent on these medications compared to PPI’s. The most researched drug of this class in the context of cancer is Cimetidine, also known as Tagamet. There is a substantial body of evidence which indicates that Tagamet is also an effective adjunctive cancer therapy1,2,3,4. The conclusion from one major study was, “These results clearly indicate that Cimetidine treatment dramatically improved survival in colorectal cancer patients with tumour cells expressing high levels of sLx and sLa.”1
An interesting double blind study was completed in 1988 which showed that survival was significantly enhanced in patients who took cimetidine 400mg two times per day for 2 years after gastric cancer surgery6. Many of these gastrointestinal cancers are stimulated by histamine and cimetidine blocks this effect7. The use of cimetidine as an adjunctive cancer therapy tends to be very indicated for gastric and colon cancers.
The exact mechanism of this anti-cancer effect is still not fully understood. Cimetidine is thought to target a class of molecules known as cadherins and by doing so it reduces the risk of metastasis. In Asia it is commonly used in conjunction with the chemotherapy 5-FU to treat colorectal cancers and this has resulted in significant increases in patient survival1. It appears that there are other pathways involved with this anti-cancer effect. Regardless of the mechanism it is clear that this medication has potential as an adjunctive cancer therapy in patients with colorectal cancer.
It is important to point out that this drug is not appropriate for everyone as there are a number of potential interactions. It is metabolized through the P450 pathway5 and this is the same pathway that many other drugs are metabolized through. This is not an absolute contraindication but you have to be careful about the dosing and often it is best to slowly introduce the Cimetidine. It is essential that you have a Naturopathic oncologist who is familiar with the use of Cimetidine look through all of your medications to determine if this is the right therapy for you.
Dr. Adam McLeod is a Naturopathic Doctor (ND), BSc. (Hon) Molecular biology, First Nations Healer, Motivational Speaker and International Best Selling Author. He currently practices at his clinic in Vancouver, British Columbia where he focuses on integrative cancer care. https://www.yaletownnaturopathic.com
1) Matsumoto, S., et al. “Cimetidine increases survival of colorectal cancer patients with high levels of sialyl Lewis-X and sialyl Lewis-A epitope expression on tumour cells.” British journal of cancer 86.2 (2002): 161-167.
2) Kobayashi, Ken-ichi, et al. “Cimetidine inhibits cancer cell adhesion to endothelial cells and prevents metastasis by blocking E-selectin expression.” Cancer research 60.14 (2000): 3978-3984.
3) Kubecova, Martina, et al. “Cimetidine: An anticancer drug?.” European Journal of Pharmaceutical Sciences 42.5 (2011): 439-444.
4) Bolton, Elaine, Julie King, and David L. Morris. “H2-antagonists in the treatment of colon and breast cancer.” Seminars in cancer biology. Vol. 10. No. 1. Academic Press, 2000.
5) Levine M, Law EY, Bandiera SM, Chang TK, Bellward GD (February 1998). “In vivo cimetidine inhibits hepatic CYP2C6 and CYP2C11 but not CYP1A1 in adult male rats”. The Journal of Pharmacology and Experimental Therapeutics 284 (2): 493–9.
6) Burtin, Claude, et al. “Clinical improvement in advanced cancer disease after treatment combining histamine and H2-antihistaminics (ranitidine or cimetidine).” European Journal of Cancer and Clinical Oncology 24.2 (1988): 161-167.
7) Adams, W. J., J. A. Lawson, and D. L. Morris. “Cimetidine inhibits in vivo growth of human colon cancer and reverses histamine stimulated in vitro and in vivo growth.” Gut 35.11 (1994): 1632-1636.