Papaverine Alprostadil

Papaverine 30 mg/mL injection Variable, usually used in combination with alprostadil and phentolamine... 

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 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. 

A 57-year-old man with erectile impotence, who had previously been treated with intracorporeal injections of papaverine and alprostadil, resulting in recurrent episodes of priapism necessitating aspiration, decided to try intraurethral alprostadil (MUSE). The dose needed to achieve a full erection in the clinic was titrated to 1 ig, but after 5 months this was found to be inadequate unless supplemented by a hot bath before MUSE administration. The patient stated that with MUSE alone the erection lasted for 5-10 minutes but on the two previous occasions when he had had a hot bath for 20 minutes and then used MUSE, the erection had lasted 3-4 hours. However, on the third occasion, priapism lasted 20 hours and necessitated corporeal aspiration for detumescence. 

The vasoactive amines phentolamine and papaverine are occasionally used as intracavernosal therapy, usually in combination with alprostadil, although their use for erectile dysfunction is off-label. Moxisylyte is another vasoactive agent used as intracavernosal therapy. The drug is approved in several European countries, but is not approved in the United States. The advantages over alprostadil are that with moxisylyte, sexual stimulation is still required to achieve full erection and that detumescence occurs on ejaculation. 

Other Agents. Phentolamine is a nonselective al- and a2-adrenoreceptor antagonist. It is a weak erectogenic agent when used alone as an intracavemosal injection. Phentolamine is usually used in combination with alprostadil and/or papaverine. 

Although many other agents, including papaverine and phen-tolamine, have been used off-label for intracavernosal therapy, al-prostadil is preferentially prescribed. This is because the FDA has approved intracavernosal alprostadil for erectile dysfunction, and because it has a low potential for causing prolonged erections and priapism. 

Reference Papaverine Concentration (mg/ml)- Phentolamine Concentration (mg/ml)- Alprostadil Concentration (mcg/ml)- Atropine Concentration (mg/ml)- ... 

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. ... 

PGE, (alprostadil) may be used in the treatment of impotence. Intracavemous injection of PGE, causes complete or partial erection in impotent patients who do not have disorders of the vascular system or cavernous body damage. The erection lasts for 1 to 3 hours and is sufficient for sexual intercourse. PGE, is more effective than papaverine. The agent is available as a sterile powder that is reconstituted with water for infections (Caverject). 

There appear to be no published reports of adverse interactions between intracavemous alprostadil (prostaglandin E,) and other drugs used for erectile dysfunction, but some manufacturers say that smooth muscle re-laxants such as papaverine and other drugs used to induce erections such as alpha-blocking drugs [e.g. intracavernosal phentolamine] should not be used concurrently because of the risks of priapism (painful prolonged abnormal erection). ... 

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