INTRACAVERNOUS INJECTION THERAPY FOR MALE ERECTILE DYSFUNCTION

Transurethral alprostadil as therapy for patients who withdrew from or failed prior intracavernous injection therapy

OBJECTIVES

Patients experiencing erectile dysfunction who fail intracavernous injection (ICI) therapy are commonly believed to have exhausted pharmacologic options. We evaluated the efficacy and safety of transurethral alprostadil (MUSE) in patients experiencing erectile dysfunction who underwent prior ICI therapy (alprostadil, papaverine, phentolamine, or a combination of these).

METHODS

Of the 1511 patients enrolled in a multicenter trial of transurethral alprostadil, 452 (30%) reported prior ICI therapy and its effects. These patients tested up to four dose levels of transurethral alprostadil in the clinic, and those who achieved an erection satisfactory for intercourse were treated at home in a double-blind, placebo-controlled trial.

RESULTS

Prior ICI therapy was reported to be "not effective" by 95 of 452 patients (21%), "sometimes effective" by 119 of 452 (26%), and "effective" by 238 of 452 (53%). In patients reporting ICI therapy as "not effective," 58% achieved an erection sufficient for intercourse following transurethral alprostadil therapy in the clinic; 47% of these responsive patients reported successful sexual intercourse after transurethral alprostadil therapy during home treatment. For patients reporting ICI therapy as "sometimes effective" or "effective," 68% achieved an erection sufficient for intercourse following transurethral alprostadil therapy in the clinic setting and 67% of these responsive patients reported successful intercourse following transurethral alprostadil therapy at home. Few adverse effects were encountered. The most common adverse effect was penile pain, which occurred with 7.8% of administrations.

CONCLUSIONS

Transurethral alprostadil therapy is an effective therapeutic option for patients with erectile dysfunction and may even "rescue" some patients who have failed prior intracavernous injection therapy.

Effects of intracavernous calcium channel blockers in dogs

Intracavernous injection of smooth muscle relaxing agents can induce penile erection. In this experimental study, we compared the effects of intracavernously injected calcium channel blockers (CCBs) and papaverine in dogs, and investigated their clinical applicabilities. We administered 30 mg papaverine, 10 mg nifedipine, 10 mg nitrendipine and 2.5 mg verapamil to 10 adult male dogs intracavernously, each at different times. Intracavernous pressure values, systemic arterial pressure values and heart rate values were recorded for 45 minutes after the intracavernous injections. We used the paired Student t-test for statistical analysis. Papaverine induced full erection in all of the 10 dogs. Nifedipine induced full erection in 4, nitrendipine in 5, and verapamil in 6 of the 10 dogs. Nifedipine and nitrendipine caused significant decreases in blood pressure and increases in heart rate. In conclusion, the effects of intracavernous CCBs are not superior to those of papaverine. We cannot recommend nifedipine and nitrendipine for intracavernous injection, but verapamil may be included in intracavernous pharmacotherapeutic combinations.

Intracavernosal forskolin: role in management of vasculogenic impotence resistant to standard 3-agent pharmacotherapy

PURPOSE

We investigated forskolin, a direct adenylate cyclase activator, as an intracavernosal vasoactive agent in management of vasculogenic impotence.

MATERIALS AND METHODS

Concentration responses for forskolin and prostaglandin E1 induced relaxation of phenylephrine precontracted strips of human corpus cavernosum smooth muscle were constructed in vitro. Cyclic adenosine monophosphate (cAMP) synthesis was determined with papaverine, phentolamine, prostaglandin E1 and forskolin in human corpus cavernosum smooth muscle cell cultures. Dose-dependent hemodynamic responses to intracavernosal forskolin (5 to 20 micrograms) were evaluated in a New Zealand White rabbit model. Safety and efficacy outcome data were obtained in vasculogenically impotent patients who signed informed consent and met strict inclusion and exclusion criteria that included having had standard self-injection therapies fail.

RESULTS

In vitro forskolin and prostaglandin E1 alone caused concentration dependent relaxation with an EC50 of approximately 200 nm. and 16 nm., respectively. When the 2 agents were combined, the concentration response curve for relaxation shifted to the left. cAMP production was highest in cells treated with prostaglandin E1 and forskolin and was unaffected by papaverine or phentolamine. In 3 animals, equilibrium intracavernosal pressure and duration of erection had a dose dependent increase. Clinical investigation in 31 patients showed no adverse events with a mean of 14 +/- 4, range 11 to 18 months of followup. Overall 61% reported improvement in rigidity and/or erection duration using intracavernosal forskolin (98 micrograms./ml.), papaverine (29 mg./ml.), phentolamine (0.98 mg./ml.) and prostaglandin E1 (9.8 micrograms./ml.).

CONCLUSIONS

Forskolin is a United States Food and Drug Administration nonapproved vasoactive agent that acts in synergism with prostaglandin E1 to induce smooth muscle relaxation. In combination with other vasoactive agents, forskolin has demonstrated preliminary safety and efficacy in patients with vasculogenic impotence resistant to standard 3-agent pharmacotherapy.

Outcome analysis of penile implant surgery after external beam radiation for prostate cancer

PURPOSE

We evaluated the success and possible complication rates of penile implant surgery in patients who underwent external beam radiation therapy for prostate cancer.

MATERIALS AND METHODS

We reviewed the charts of 43 patients who underwent penile implant surgery after radiation therapy for prostate cancer. The type, dose and volume of radiation were assessed. The types of surgical approach and prosthesis as well as complications were recorded. A total of 34 patients was alive and traceable, and 9 were untraceable (7 dead and 2 missing). The 34 traceable patients were interviewed personally or by telephone to evaluate the function of and satisfaction with the penile implant. Followup of the 9 untraceable patients was assessed through a chart review.

RESULTS

A total of 35 patients (81%) received definitive radiation therapy to the prostate and seminal vesicles, and 8 (19%) underwent radical retropubic prostatectomy followed by radiation therapy to the prostatic bed. Mean age at implant surgery was 67 years (range 36 to 83). In the 43 men 46 procedures were done and mean followup was 40 months. None of the patients in this series had infection or erosion. Of the men 24 (71%) use the prosthesis at least once weekly or more for sexual intercourse, 6 (17%) use it twice monthly, 4 (12%) are not sexually active despite a functioning implant, 2 are not sexually active because of a lack of sexual partners, and 2 are not satisfied with the implant and would not recommend this device. Discomfort from the penile implant was reported by 2 patients, although they currently use the implant for intercourse at least twice weekly.

CONCLUSIONS

Penile prosthesis surgery can be safely and effectively performed after radiation therapy with minimal intraoperative and postoperative complications, and an excellent patient satisfaction rate.

Influence of the method of intracavernous injection on penile rigidity: a possible pharmacokinetic explanation

OBJECTIVES

To study whether the method of intracavernous injection of vasodilators has an effect on the clinical outcome and to explain the mechanism of possible influence.

METHODS

In an open clinical study, penile rigidity after bolus injection was compared with rigidity after slow injection in 52 self-injecting, impotent patients. In 35 volunteers, venous plasma levels of intracavernosally injected drugs were followed under different injection conditions: slow injection of undiluted drug, slow injection of diluted drug, bolus injection, use of a tourniquet, or slow injection followed by squeeze of the corpora.

RESULTS

Of the 52 patients, 28 reported better penile rigidity after a bolus injection than after slow injection of vasodilators. The other 24 reported no difference in rigidity. Systemic side effects did not occur, but 4 patients reported local pain after bolus injection. In the 35 volunteers, the lowest plasma levels were observed when a tourniquet was used or when a bolus injection was performed; the quickest transfer was observed after a slow injection of a low volume of the drug.

CONCLUSIONS

Better rigidity was observed after bolus injection in a majority of the patients using the same dose of vasodilators. This could be due to the pharmacokinetic phenomenon of a slower drug transfer to the systemic circulatory system after a bolus than after a slow injection.

Intracavernosal Injection Therapy and Other Treatment Options for Erectile Dysfunction

In the United States, almost 30 million men have complete or partial erectile dysfunction. This disorder occurs in approximately 52% of men between 40 and 70 years of age; 70% of affected men younger than 35 years of age have psychogenic causes, and 85% of men older than 50 years of age have organic impotence. Furthermore, erectile dysfunction is exacerbated by the presence of such conditions as heart disease, diabetes, and hyperlipidemia and the medications used to manage them. Thus, a widespread segment of the population is in need of a safe and effective treatment strategy for restoration of normal sexual function. The technique of intracavernosal injection therapy was initially described in the early 1980s. During the subsequent decade, the effectiveness of various drug combinations and the associated side effects were demonstrated. In 1995, prostaglandin E(1) was approved for intra-cavernosal pharmacotherapy. It has proved highly effective for neurogenic, vasculogenic, and psychogenic erectile dysfunction, with reported response rates of 75 to 92%. The major side effect (albeit uncommon) is corporal fibrosis. Other options for treatment of erectile dysfunction are vacuum-erection devices and penile prostheses.

Intracavernous pharmacotherapy

Intracavernous application of vasoactive substances not only has enhanced our understanding of penile hemodynamics, the physiology of penile erection, and the pathophysiology of erectile dysfunction but also has revolutionized the diagnosis and treatment of erectile dysfunction in the last 15 years. Virag was the first to report on the erectile effect of papaverine in humans, and Brindley later reported the effect of intracavernous application of alpha-receptor-blocking agents on cavernous tissue. These reports led to numerous basic and clinical investigations and ultimately established a new treatment alternative for patients with erectile dysfunction that is now considered to be the treatment of choice for most patients. Changes in penile hemodynamics include the relaxation of cavernous smooth musculature and arteries, which leads to an increase in arterial blood flow and a restriction of venous outflow through a compression of subtunical veins. These hemodynamic changes are the prerequisite for the induction and maintenance of penile erection. With the intracavernous application of vasoactive substances it was possible to influence penile hemodynamics at a local level and to induce an erection despite alterations in the nervous system, penile arterial blood flow, cavernous musculature, or neurotransmitter status. In addition, the local application of pharmacologically active substances directly to the end organ enabled the achievement of high local drug concentrations without severe systemic side effects. The commonly used substances are papaverine the combination of papaverine and phentolamine, and prostaglandin E1 (alprostadil). In addition to these established substances, several other regimens, such as linsidomine (SIN-1), calcitonin gene-related peptide (CGRP), moxisylyte, and various triple- or quadruple-drug mixtures have been described. In addition, several other compounds as well as different routes of administration are on the horizon and may prove to be effective in the future diagnosis and treatment of erectile dysfunction.