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Researchers at the University of York in the United Kingdom today published data showing the existing anti-epilepsy drug phenytoin (Dilantin) may fight breast cancer. They have completed in vitro (e.g. using a petri dish) tests, as well as animal tests, but have yet to test their findings in humans.

Phenytoin (Dilantin)

The sodium channel-blocking antiepileptic drug phenytoin inhibits breast tumor growth and metastasis

Phenytoin is a sodium-channel blocking drug, developed over 100 years ago, and was popularized as an anticonvulsant because of it’s lack of sedative effects, especially compared to phenobarbital. It was first approved by the US FDA in 1953 and thus is no longer a patented drug.

The lead researcher, Dr. Willi Brackenbury, wrote “This is the first study to show that phenytoin reduces both the growth and spread of breast cancer tumour cells. This indicates that re-purposing antiepileptic and antiarrhythmic drugs is worthy of further study as a potentially novel anti-cancer therapy.”

In November, 2014, Brackenbury and other researchers announced a new human study in breast, bowel, and prostate cancer patients, to study overall survival in patients using sodium channel-blockers like phenytoin.

Curiously, several anticonvulsant drugs have also shown anticancer properties, especially valproic acid (Depakote). Valproic acid happens to be a powerful HDAC inhibitor, limiting the cell cycle transition of cancer cells and helping the expression of beneficial proteins. In particular, HDAC inhibitors have been shown to be radiosensitizing agents, which have already shown in human studies to improve survival in cancer patients undergoing radiation therapy. Previously-approved drugs from other medical conditions which are used for their anticancer properties are referred to as off-label drugs.

Another popular anticonvulsant strategy not involving drugs is the ketogenic diet, in which patients eat a diet rich in fat and low in carbs, similar in practice to popular diets such as the “Atkins” and “South Beach” diets. The Epilepsy Foundation explains, “Several studies have shown that the ketogenic diet does reduce or prevent seizures in many children whose seizures could not be controlled by medications.” The Foundation notes that ketogenic diets are usually not recommended for adults simply because “the restricted food choices make it hard to follow.” It’s not well understood why this diet helps control seizures.

Ketogenic diets for cancer patients, often involving fat/carb ratios approaching 4:1, strive to reduce the amount of glucose available to power cells, forcing the cells to convert energy from ketones instead. Cancer cells can not metabolize ketones, and thus die. Many researchers have explored ketogenic diets as an anticancer therapy for decades, however, since there is no patent for pharmaceutical companies to capitalize on, it’s difficult to fund trials in humans. For more information about ketogenic diets, and commercial supplements which help patients find a nutritionally sound method of using the diet, patients should consult their doctor as well as several available books on the subject.