Medical uses for erectile dysfunction drugs
Researchers at Cedars-Sinai Medical Center are testing the medication tadalafil (sold as an erectile dysfunction drug under the brand name Cialis) on men with Becker muscular dystrophy, one of the nine forms of muscular dystrophy, a group of inherited muscle-wasting diseases.
Here's a description of the small trial planned by Dr. Ronald G. Victor of Cedars and colleagues, which is being funded by the Muscular Dystrophy Assn. Twenty-four men with Becker's will receive either two doses of a placebo or the drug, and then researchers will measure the degree of blood flow to the muscles that occurs when the men are exercising. It follows from research in which mice with animal versions of muscular dystrophy could exercise more vigorously and with less muscle damage when they were given the drug.
Since tadalafil dilates blood vessels, and since in that muscular-dystrophy-mouse study the damage to muscles appeared to be related to a lack of blood supply, the trial makes some kind of sense.
And if so, it would be just one of a number of potential medical uses for erectile dysfunction drugs, which are kind of coming full circle, it seems.
Here's some information about that from a history of the drug published in 2006 by the journal Nature Reviews Drug Discovery. (Sorry, but the journal requires payment to access anything more than the abstract.)
The first of these drugs, sildenafil (Viagra) was stumbled upon during early human tests of a potential angina drug (then known merely as UK-92,480) by scientists at the drug company Pfizer. Researchers learned that people in the trial were reporting erections.
Intrigued, scientists launched trials designed specifically to test the sexual effects, in which erections were measured using a "Rigiscan" device -- loops placed over penises to gauge how hard and erect they got upon sexual stimulation.
(Even later on, an "International Index of Erectile Function" was designed and used in clinical trials.)
Since 2005, sildenafil has been FDA-approved under the brand Revatio for the treatment of pulmonary hypertension, a condition of high blood pressure in the arteries of the lungs.
And the authors of the Nature Reviews Drug Discovery point to studies suggesting sildenafil or similar drugs might potentially help diseases such as congestive heart failure, hypertension, stroke and certain other lung disorders.
"Moreover," they write, "many years after the original indication was abandoned, single-dose sildenafil was shown to prolong exercise time in men with angina."
And this: "Although these findings might seem to be quite disparate and unrelated, all of the disorders
described above are in fact characterized by regional deficiencies in blood supply."
— Rosie Mestel