Can digoxin help in treatment of prostate cancer?

An article in the new journal Cancer Discovery has suggested that the drug digoxin (originally derived from foxgloves, and also known as digitalis) may have utility in the management of prostate cancer.

Platz et al. carried out a two-part study designed to explore the value of drugs already on the market for other indications in the management of prostate cancer.

In the first part of this study, the research team carried out a classic in vitro cytotoxicity screen of 3,187 compounds to see if these compounds had potential activity against prostate cancer cells in the laboratory. They were able to show that digoxin had a significant level of potency in inhibiting proliferation of prostate cancer cells in vitro, and they already knew that digoxin had a long history of use in the management of cardiovascular diseases such as congestive heart failure and arrythmias (although its use is much less common today than it was a decade ago).

In the second part of the study, Platz and her colleagues looked at data on the use of digoxin and prostate cancer risk in a cohort of 47,884 men followed from 1986 through 2006 in the Health Professionals Follow-up Study. They found that regular digoxin users had a significantly lower incidence of prostate cancer (relative risk [RR] = 0.76) compared to non-users. They also found that this relative risk was even lower among men who had been treated with digoxin for 10 years or more (RR = 0.54). Overall, use of digoxin was associated with a 25 percent lower prostate cancer risk.

The objective of the study by Platz and her colleagues was not actually to try to find new drugs for prostate cancer. Rather, it was to establish the process of evaluation of older drugs for their potential in the treatment of disorders for which they had never previously been tested. Additional information is available in an article in Prostate Cancer Discovery on the Brady Urological Institute web site at Johns Hopkins.

However, this now raises the question of whether digoxin should, in fact, be tested for its ability to manage prostate cancer. Digoxin is not a drug one would expect to give to otherwise healthy male patients, because it has a long history of concentration-dependent side effects. However, a more serious question is going to be whether digoxin could actually have the ability to delay the progression of prostate cancer in men with early stage disease — either on its own or in combination with other forms of treatment. If the plasma level of digoxin is kept below about 0.8 μg/l, and use of the drug is avoided in patients with low levels of serum potassium, then the side effects of digoxin can usually be avoided.

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