Stendra® (Avanafil)- New Erectile Dysfunction Medication
April 27th, 2012 the FDA (United States Food and Drug Administration) accepted Stendra for the treatment of Erectile Dysfunction. Its main benefit is that clinical studies have shown it to work in as little as 15 minutes after being taken. This is around twice as fast as other current treatments.
Erectile dysfunction is a very common condition, with between 15 to 30 million in the United States suffering from it: it is estimated that 1 in 10 men across the world experience it. In the age group of forty years, almost half of men have it (40%): by the time men reach sixty five, 65% of them will have it.
Many factors in today's world contribute to men experiencing erectile dysfunction: the fast pace of life, worry about finances, stresses in the workplace, and the fact that there never seem to be enough hours in the day. Erectile dysfunction has a devastating effect on the sufferers. Their quality of life is reduced: their intimate relationships suffer, their self-esteem is dented, and they have to cope with yet another challenge on top of everything else. So there is a great need for assistance from the medical profession.
Following a great deal of research over the last twenty years or so, several medications have been developed. The best results have been found from the phosphodiesterase type 5 (PDE5) inhibitors. These work by inhibiting the enzyme which suppresses the dilatation of the smooth muscled in blood vessels, so blood flow to the penis is increased, facilitating the attainment and maintenance of an erection.
The first PDE5 inhibitor, sildenafil, released under the trade name Viagra, was very effective in treating erectile dysfunction but also increased blood flow to other smooth muscle. This tended to cause headaches and flushing of the skin. Some sportspeople in fact use it to enhance their sports performance because of the improved blood flow to their muscles.
Since then other PDE5 inhibitors have been developed, and some of these target the penis more, so have less effect on other smooth muscles. Some of them are vardenafil, marketed as Levitra®, and tadalafil, sold as Cialis®.
Vivus Inc currently received an FDA approval for its medication, another PDE5 inhibitor called avanafil, trademarked as Stendra. This has a distinct advantage over the others in its group in that its onset of action is much more rapid. Some men experienced a good erection only 15 minutes after taking it, and others within 30 minutes. By comparison, the other PDE5 inhibitors take much longer to work. Tadalafil takes more than 30 minutes to reach full plasma levels, so ideally should be taken by the patient at least 45 minutes before he wishes to achieve an erection. Sildenafil needs to be taken 1 hour before the effect is required and the same with vardenafil.
The phase 3 clinical trials for Stendra included 646 men. The drug was tested in doses of 50 mg, 100mg and 200mg. It was found that there was improvement in erections at all doses, and that nearly 80% of doses resulted in an erection of a good enough quality for intercourse to take place when the highest dose of 200 mg was administered. The window of opportunity was found to be more than six hours.
Avanafil (Stendra®) is also reported to have a very low incidence of side effects, partly because it is highly selective, so targeting only the required areas, and also as its half-life is relatively short, meaning that it is cleared from the body faster than the other PDE5 inhibitors. The side effects included, as with the others in the class, headaches (in 7% of men), skin flushing (in 4.6%) and nasal congestion (in 2.3%). No visual complications, found with sildenafil, were observed. No serious drug-related effects were observed, which means that this is a very safe drug to use.
Apart from the current phase 3 trial, there are three others ongoing as well. These examine avanafil's usefulness in treating erectile dysfunction in men with diabetes and following prostate surgery, and a general clinical trial with 400 subjects across the USA.
There are indications that avanafil may be of clinical value in the treatment of some other conditions such as hypertension, emboli, female lack of libido , Alzheimer's disease, and the treatment of strokes due to blood insufficiency to parts of the brain. The utilisation of avanafil in these conditions is not yet being explored in clinical trials but it is quite possible that such trials may be commenced in the not too distant future.
The application for review of avanafil was submitted to the Food and Drug Administration in September 2011, and we are pleased to see that the FDA accepted it..
In view of its greater selectivity and its rapid action, it is expected that avanafil's entry into the market will be greeted with great enthusiasm. Its only real competition would then be the entry into the market of generics of sildenafil, when the patent expires during 2012, opening the door for cheaper generics.