About Erectile Dysfunction Vasoactive drugs may also be injected intracavernosally. Such therapy represents an important second-line therapy for erectile dysfunction. It is the most effective pharmacologic treatment but has a high dropout rate because of the associated pain and apprehension involved. Phentolamine is an -blocker that was used in initial studies; its efficacy is poor, but it may be used in combination with other agents. Papaverine is a nonspecific PDE inhibitor and was the first effective intracavernosal therapy for erectile dysfunction. Currently, intracavernosal alprostadil therapy is preferred; it is more effective than other agents and produces fewer side effects. In a comparison study comparing alprostadil, a papaverine–phentolamine combination and papaverine alone, rates of success (ability to achieve and maintain an erection) of 72%, 61% and 31% were reported respectively.54 No patients in the alprostadil group experienced priapism, as compared with 2% and 4% of patients in the combination therapy and papaverine-only groups respectively. On the other hand, patients who used alprostadil were the only ones to report penile pain. For patients who do not respond to or do not tolerate alprostadil monotherapy, a triple mixture of papaverine, phentolamine and alprostadil may be prescribed. Such combination therapy has been shown to be more effective and, because of a lower dose of alprostadil, results in less pain.62 Complications of intracavernosal injections include pain, priapism and fibrotic changes at injection sites. Horwitz said he and his colleagues plan to take the current research to the next level. looking for viagra without prescription? viagra without prescription