Cimetidine and Other H2 Blockers

People with colorectal cancer treated with cimetidine before, during, or after surgery showed better survival after surgery in a number of studies. However, a few studies found that benefits were limited to people with certain types or stages of colorectal cancer. One study found better survival after surgery for people with colorectal cancer treated with ranitidine, but only those who didn’t receive blood transfusions or develop infections.

People with advanced cancer treated with histamine and H2 blockers showed longer survival and better function in a small study. Another small study found that people with advanced ovarian cancer treated with cimetidine and platinum-based systemic chemotherapy had better prognosis and survival after surgery.

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In a few small studies, people with cancer treated with cimetidine, usually around the time of surgery, showed higher markers of immune activation.

In one small study, people with B cell chronic lymphocytic leukemia treated with ranitidine and vaccinated for a type of bacterial infection (Haemophilus influenzae type-B) showed better vaccination response.

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People with non-small cell lung cancer treated with gefitinib and H2 blockers showed less liver dysfunction than those treated with gefitinib alone in a small study.

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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). However in the same study, people using H2 blockers for less than one year showed moderately increased risk of these cancers.

In an analysis of 3 studies of people using H2 blockers after removal of colorectal adenomas, no effect was seen on risk of recurrence. Adenomas are benign tumors that can become cancerous.

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• Not mentioned in cancer clinical practice guidelines for cancer care
• Limited use by our program sources

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• Increased risk of breast and lung cancers with use
• May raise estrogen levels
• Linked to worse survival among people using H2 blockers treated with PD-1/PD-L1 inhibitors but no effect on gefitinib, Interleukin-2 (IL-2), or ALA-PDT
• Side effects of use are usually mild, but some serious side effects are possible.
• Cimetidine may interact with several medications and therapies.

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• Available both by prescription and as an over-the-counter drug
• Moderate cost (between $500 US and $2000 US/year)

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