Better Erections with Injections

Historically, the concept that a penile erection could be initiated by injection of drugs into the erectile tissues was introduced to urologists at the annual urology convention in the spring of 1983 in Las Vegas at an evening seminar attended by several hundred urologic physicians. The invited speaker, Dr. Giles Brindley, lectured on the physiologic and pharmacologic innovations in the undertstanding of penile erection. Unbeknownst to the audience, Dr. Brindley injected his penis with a long-acting alpha-blocker drug, phenoxybenzamine, prior to the lecture. During the lecture, Dr. Brindley showed many slides of his own penis in various states of penile erection after the administration of various oral and subcutaneous medications. At the end of his lecture, Dr. Brindley removed his pants (he wore jogging pants) and displayed to the alarmed audience that he had a penile erection induced by the injection. Although this was an unusual presentation, Dr. Brindley did usher in a new era – the use of pharmacologic agents to induce functional erections for the treatment of erectile dysfunction. We had patients on self-injection therapy 1 week after the Dr. Brindley demonstration.

It is now 21 years later and, in the Institute, we have over 5000 men who use self-injection therapy as a successful, reliable strategy for the treatment of ED. As it was in 1983, the use of self-injection therapy remains an “amazing” therapy.

Self-injection therapy is based on the physiologic understanding of the mechanism of penile erection. To have a physiologic erection response, there are basic requirements. Arterial blood inflow is regulated by smooth muscles within the tiny arteries called “helicine arterioles”. Relaxation of these smooth muscles results in a large increase of blood inflow to the erectile tissues. Veno-occlusive trapping of the increased blood inflow within the confines of the corpora cavernosa is regulated by different smooth muscles, those surrounding the blod filled spaces within the erectile chamber. Relaxation of these smooth muscles results in engorgement of the erectile tissues with subsequent stretching and compression against the tunica albuginea of the small outflow veins called “sub-tunical venules”. The result of the two smooth muscles undergoing relaxation is a penile erection. The key to self-injection therapy is that the injected medications induce sustained penile smooth muscle relaxation.

The Institute’s male RN, Terry Payton, has been teaching patients self-injection therapy since the spring of 1983. He is very knowledgeable and well-recognized for his expertise in this area of ED treatment. Self-injection therapy is indicated for erectile dysfunction that is unresponsive to oral agents, psychologic therapy, vacuum constrictive device therapy, and where other therapies are not considered safe or appropriate (e.g. a man who is on nitroglycerine is not a candidate for treatment by oral pill use). Typical clinical situations where a man with ED problems would consider self-injection therapy includes ED after prostate cancer treatment, ED after low spinal cord injuries, ED with multiple sclerosis, ED with Peyronie’s disease, ED with accompanying venous leak (veno-occlusive dysfunction).

A typical injection involves use of a 30 or 31 gauge insulin needle. The medication typically utilized consists of various combinations and doses of three agents: papaverine hydrochloride, phentolamine mesylate and prostaglandin E1. Prostaglandin E1 alone (Caverject, Edex) is an FDA approved therapy for ED. Individual patients usally need a series of office injections to identify which agent (s) work best for them. The goal is to obtain a functionally rigid erection for approximately 30 – 60 minutes. The drugs are injected into the side of the stretched penile shaft. After injection, tight compression of the penile shaft in a fist for three minutes helps prevent bleeding inside the penile tissue which may lead to internal penile scar formation.

The major complication is a sustained erection lasting more than 4 hours. For this situation, injection of the antedote, phenylephrine, leads to detumescence of the erection.

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of BU School of Medicine