Cimetidine is a commonly used over-the-counter drug that treats heartburn and other gastric disorders that is also sold under the brand name Tagamet®. The possible use of cimetidine for cancer was discovered in the 1970s when several cancer patients who were taking cimetidine for heartburn improved spontaneously, spawning several decades of research into the mechanisms behind this phenomenon. Some studies have yielded that cimetidine appears to cause some improvement in the conditions of many cancer patients and may help slow the spread of cancer, especially in certain gastric cancers and combined with additional treatment. The outcomes of these studies suggest that more research is needed, however, as of 2011. Still, many cancer patients turn to cimetidine for cancer as a supplementary treatment because it is inexpensive, easy to obtain, and relatively safe to use over long periods.
The benefits of cimetidine for cancer victims were first postulated in 1979, two years after cimetidine was first approved by the US Food and Drug Administration and three years after it first appeared in the United Kingdom. Researchers first became interested in researching the use of cimetidine for cancer after cancer patients who were taking the drug for gastric issues experienced improvements in their conditions. This spawned a study of lung cancer patients that indicated that cimetidine appeared to have anti-tumor activity. Over the next two decades, many studies in mice and human subjects followed.
In 2002, a Japanese study followed two groups of colon cancer patients. One group received 5-fluorouracil and cimetidine, while the other group received only 5-fluorouracil for nearly a year. The 10-year survival rate of the cimetidine group approached 85 percent, while the non-cimetidine group was around 50 percent. The researchers noticed that the greatest effectiveness of cimetidine for cancer was against cells that expressed the greatest amounts of sialyl Lewis antigens, which control cell-to-cell recognition and help attract certain types of cells to each other.
A UK study attempted to determine the mechanism behind the perceived effectiveness of cimetidine for cancer. Researchers postulated that the drug improved the immune systems of cancer patients while preventing cancer cells from adhering to the epithelium. Results supported this hypothesis. Put simply, cimetidine appears to help prevent cancer from spreading and metastasizing to other areas of the body.
Colorectal tumors contain high amounts of histamine, which is believed to stimulate the tumor growth. Cimetidine may act by changing the way histamine acts on tumors, inhibiting tumor growth. Still, there are other drugs that act in the same way against histamine as cimetidine that lack its effectiveness, so the exact pathway for its effectiveness may have yet to be discovered. In the years since these studies, other research has supported initial findings, and new research has shown that cimetidine is effective against other types of cancers.
As a treatment for cancer, cimetidine has not been approved by the US Food and Drug Administration as of 2011, yet it is often considered a safe, affordable, alternative treatment that can be used in conjunction with traditional chemotherapy drugs and surgery. Side effects are mild and usually well tolerated. Although the drug is not recommended for long-term use, some doctors claim it is safe to use for the duration of cancer treatment. As with any drug, cimetidine should not be taken for purposes other than its intended use except under the advice of a qualified physician.