Injection and Intraurethral Treatments
Penile injection therapy was developed and reported in human trials in 1982 by Virag. Dr. Giles Brinley shocked AUA audience members in Las Vegas in 1983 when he removed his pants to show his chemically induced erection. Initial trials with papaverine and phentolamine as single agents caused penile scarring, which eventually led to Goldstein and colleagues (1990) pioneering the currently accepted combination of papaverine, phentolamine, and prostaglandin E-1, known as trimix, in 1990. Eventually, the FDA approved alprostadil for injection in 1995 as Caverject® and in 1997 as Edex®. All of these options for injections are delivered directly to the penile corpora via needle. Vital evaluation points when suggesting these injections for use are that patients have the manual dexterity to self-inject, and can visually or tactilely identify the accurate location of injection. Partners can also be taught to administer injections.
Intraurethral alprostadil (Muse®) was FDA-approved in 1996 and works similarly to the injectable form by causing smooth muscle relaxation and vasodilation, but is delivered transurethrally. During in-clinic testing of 1,511 patients treated with Muse, 65.9% of men had erections sufficient for intercourse (Padma-Nathan et al., 1997). Clinicians have found that in practice, in patients with varying etiologies, the efficacy is lower than in initial studies.
Efficacy with Muse may improve when combined with one of the PDE5 inhibitor oral agents, and the efficacy of Muse increases with the addition of Viagra (Nehra & Goldstein, 1999). In the study by Nehra and Goldstein (1999) of 26 men with ED who had failed either 100 mg sildenafil and/or 1,000 mg Muse (26/26), patients reported erections sufficient for vaginal penetration at 18 months, and none had crossed over to injection therapy or penile prosthesis.
Urol Nurs. 2019;39(5):262-264. © 2019 Society of Urologic Nurses and Associates