Priapism with intracavernosal alprostadil

Intracavernosal alprostadil has been used successfully in combination with VEDs or vasoactive agents (e.g., papaverine, phentolamine, atropine) that act by different mechanisms. Phosphodiesterase inhibitors should not be added to intracavernosal alprostadil because the combination can cause prolonged erections and priapism. 

Intracavernosal alprostadil was effective and well tolerated in the treatment of erectile dysfunction, according to the results of a 6-month study (funded by Pharmacia Upjohn) in 848 men (mean age 52 years) with at least a 4-month history of erectile dysfunction (12). This is provided that the individual dose is established by titration and patients receive training in injection techniques and periodic supervision during treatment. An initial dose was established for each patient and the patients then administered the alprostadil themselves at home. Of 727 evaluable patients, 682 (94%) had at least one erectile response after the injection of alprostadil, and 88% of injections lead to a satisfactory sexual response. The most commonly reported adverse event was penile pain, reported by 44% of patients, but only after 8% of injections. In just over half of the patients who had penile pain, the condition was reported as mild. Prolonged erection, penile fibrosis, and priapism occurred in 8,4, and 0.9% of patients respectively. Treatment was withdrawn because of medical events in 4% of patients, and drug-related events accounted for treatment withdrawal in 2% of patients. 

Although intracavernosal alprostadil injections are effective independent of the etiology for erectile dysfunction, these fail in one-third of patients. Also, they should be used cautiously in patients at risk of priapism, which includes those with sickle cell disease or lymphoproliferative disorders. 

Intracavernosal injection or urethral suppository therapy with alprostadil (PGE1) is a second-line treatment for erectile dysfunction. Doses of 2.5-25 meg are used. Penile pain is a frequent side effect, which may be related to the algesic effects of PGE derivatives however, only a few patients discontinue the use because of pain. Prolonged erection and priapism are side effects that occur in less than 4% of patients and are minimized by careful titration to the minimal effective dose. When given by injection, alprostadil may be used as monotherapy or in combination with either papaverine or phentolamine. 

Papaverine is not FDA approved for erectile dysfunction. Intracavernosal papaverine alone is not commonly used for management of erectile dysfunction because large doses are required, and these produce dose-related adverse effects priapism, corporal fibrosis, hypotension, and hepatotoxicity. Papaverine is more often administered in lower doses combined with phentolamine and/or alprostadil. A variety of formulae have been used, but no one mixture has been proven better than other mixtures (see Table 81-6). Combination formulations are considered to be safer and associated with the potential for fewer serious adverse effects than high doses of any one of these agents. ... 

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