Viagra is still the rage. But one should pop the pill just before sex. The anxiety could even spoil all the fun. Now some good news for those suffering from erectile dysfunction (ED) - gene therapy. And it could be effective far longer than the pills.
Human and animal trials suggest gene therapy could offer a credible alternative to the current treatments available. A University of Pittsburgh team, led by Dr Joseph Glorioso, tested an experimental gene therapy in rats with ED caused by nerve damage. The gene therapy used comprised the herpes simplex virus as a carrier and either a gene called GDNF, or one called neurturin, which both help promote nerve growth.
Rats treated with the gene therapy showed significant recovery and were able to regain normal penile function after four weeks.
ED, often referred to as impotence, means inability to get a good enough erection to achieve satisfactory intercourse, but it varies in severity.
There are many causes, and many effective treatments, including drugs like the three licensed in the UK - Viagra, Cialis and Levitra.
But not all types of ED respond well to medication - for example, ED caused by nerve damage following prostate cancer surgery. US researchers are hopeful that for these patients, and those who experience side-effects with medication, gene therapy may be a good alternative.
Meanwhile, scientists at Wake Forest University, with the help of Dr Arnold Melman from the Albert Einstein College of Medicine, have been conducting the first human study of gene therapy for ED. Tests on 11 men with ED showed promising results. The treatment was well-tolerated, with few side effects, despite its delivery via an injection into the penis. Although the primary goal of the study was to determine its safety, it also showed the therapy improved erectile function in some of the men.
Dr Melman said: 'This is an exciting field of research because current treatments for men with erectile dysfunction, whether pills or minimally invasive therapies, must be used 'on demand', thereby reducing the spontaneity of the sexual act.' The Wake Forest therapy works by inserting small pieces of DNA into cells to trigger the production of proteins which, in turn, help smooth muscle cells relax.
Relaxing the smooth muscle in the penis allows it to fill with blood and achieve an erection. Dr Geoff Hackett, president of the British Society for Sexual Medicine, said the gene therapy might be appealing to some men for whom other treatments had failed, but predicted many men would be reluctant to have a shot in the penis. He stressed that many men with ED also had underlying medical disease, such as high blood pressure, raised cholesterol or diabetes, and that this should also be treated.
This is an exciting field of research because current treatments for men with erectile dysfunction must be used 'on demand', thereby reducing the spontaneity of the sexual act
Researcher Dr Arnold Melman. However, the human trials involved injections into the penis and some experts queried whether men would choose this option.