Overall, relatively few RCTs of therapies for ED have been performed in the SCI population, with the notable exception of PDE5i use. That said, however, and not withstanding the issues with research designs, there is much that can still be gleaned from these case series and pre-post studies regarding differences between the efficacy, practicality and safety of each method to help guide individual decision-making and choice.
PDE5i is recommended as the first choice for treatment of erectile dysfunction in SCI, as its effectiveness has been shown to be excellent in the SCI population (about 70 – 80% success). The longer acting tadalafil may be advantageous in those men where sildenafil failed or for those wishing for more spontaneous activity (longer action of up to 24-36 hours versus 1-4 hours with Viagra and Levitra). In general, PDE5i works best on those with UMN lesions in comparison to those with LMN lesions whose nitric oxide release at the nerve end terminal may not be as consistent. A lesion above the sacral spinal tract and a higher reflexive erection are predicable favorable parameters for a positive response to all PDE5i. Effectiveness of sildenafil in men with LMN is reported to be between 28% -50% (Del Popolo et al. 2004, Khorrami et al. 2010). Short term side effects are approximately the same as with able-bodied men (headache and flushing between 10-15%, dyspepsia about 5% and visual disturbances noted in higher doses), but caution should be used in differentiating the side effects of the PDE5i with those seen with autonomic dysreflexia (AD) – especially the presence of headache so as not to ignore the symptoms of AD. The use of PDE5i is contraindicated in men taking nitrates, and should be used with relative caution in men with symptomatic hypotension and/or tetraplegia due to the native hypotensive effect of PDE5i. Long term side effects have not been evaluated in the SCI population, but it appears tachyphylaxis is rare.
At the present time, there is not enough evidence to suggest either sublingual apomorphine or oral fampridine-SR are useful in the SCI population for the treatment of ED. Injectable medications have better efficacy (90%) than PDE5i, but are more invasive, and have a higher risk of short term side effects, especially prolonged erection in the SCI population (Deforge et al. 2004a). Careful teaching of correct injection technique and dose titration can largely eliminate this problem. PGE1, papaverine and phentolamine all require refrigeration, with PGE1 being the least stable at room temperature (Deforge et al. 2004b). Prolonged use of papaverine is more likely to cause cavernosal fibrosis due to its low pH of 3-4, and therefore is more commonly used in conjunction with other medications (commonly phentolamine or atropine). Injection with any of these medications can cause subcutaneous hematomas, cavernosal or tunica fibrosis (usually small and reversible with time) or mild edema. The use of intraurethral prostaglandin (MUSE®) and topical preparations have not been that successful in the SCI population and therefore are rarely used. Penile implant surgery is reserved now for those men with failed or unacceptable reversible methods (ICI, oral therapy or vacuum device), although some men with difficulties attaching external drainage devices may find penile implants helpful.
Oral PDE5i is the first line treatment for ED in men with SCI, with the more invasive but successful use of ICI being used most often in men who do not respond to the oral medications. Mechanical devices such as vacuum devices and rings may be effective but are not as favoured by consumers. Surgical prostheses should be reserved for refractory cases. Other therapies (e.g., nitrogycerine, intraurethral and topical application of PGE1 and papaverine, sublingual apomorphine, and oral fampridine) have not proven viable when compared to the more established therapies.