Pentoxifylline is an old oral prescription drug which is indicated to improve blood flow in the lower extremities of people with vascular disease. It has been found to have a non-specific phosphodiesterase-type inhibitor effect. This makes it somewhat like a non-specific form of Viagra. The critical part is that by its effect on increasing the amount of available nitric oxide, that this can have anti-fibrotic (anti-scarring) effects. Therefore, agents such as pentoxifylline, L-arginine and the type 5-specific phosphodiesterase inhibitors (Viagra, Cialis, Levitra) all have been shown in experimental models to reduce the production of scar in an animal model of Peyronie’s disease. L-arginine in particular is the precursor to nitric oxide and therefore, is felt to potentially increase the amount of available nitric oxide. L-arginine is an over-the-counter, relatively inexpensive amino acid.
Collagenase is an enzyme which breaks down collagen. There are many different types of collagenases, but only a few works in mammalian systems to breakdown the type of collagen we find in human scar. At this time, there is research ongoing to study the use of collagenase made by a bacterium known as Clostridium. This is a non-specific collagenase which will break down all types of collagen and is very toxic when not used properly. Therefore, the clinical trials will be very carefully monitored by the FDA. There have been delays in the development of the trials by the sponsoring company, but it is hoped that by the end of 2007 that phase II trials will begin. Collagenase was first reported as a possible treatment for Peyronie’s disease as an intralesional injection in the 1980s. Unfortunately, the studies done over the past 20 years have been weak and have not been readily accepted by the FDA.