Self-injection devices for intracavernosal pharmacotherapy: operational classification and safety considerations

Several self-injection devices have been recently proposed as an aid to home intracavernosal self-injection treatment for erectile dysfunction, with the purpose of allowing an easier drug administration, decreasing the artificiality of intracavernosal pharmacotheraphy, with the overall goal of increasing the acceptability of this treatment. We propose a classification of these devices according to the type of mechanical impact on the cavernosal tissue: self-injection pens, allowing for manual needle insertion and manual drug delivery; autoinsertors, with automatic needle insertion and manual drug delivery, and autoinjectors, that provide both automatic needle insertion and automatic drug delivery. The use of autoinjectors bears two theoretical risks: extra-corporal drug delivery in cases of wrong injection site, and trabecular damage due to high delivery pressure. In one device pressures 15 times higher the values reached by manual injection, and statistically higher than pressures obtained by maximal strength manual injection, were observed in an in-vitro investigation. Specific studies are needed to define a threshold pressure value for trabecular damage in the flaccid state; accordingly, information on autoinjector developed pressures should be provided by manufacturers. Clinical studies with adequate follow-up are needed as well, to verify the risk of autoinjector-induced extracorporal drug delivery, and the occurrence of intracavernosal nodules or penile curvature, compared to manual self-injection.