Is the volume injected a parameter likely to influence the erectile response observed after intracavernous administration of an alpha-blocking agent?

In 12 impotent patients with spinal cord injury, we assessed the erectile response induced by intracavernous administration of 20 mg moxisylyte dissolved in 4 different volumes of solvent. We tested successively in each patient 0.4, 0.8, 1.2 ml and the volume usually injected of 2 ml, with a 7-day interval between 2 injections. The reduction in the volume from 2 to 0.4 ml did not thwart the quality of erection obtained by the intracorporeal administration of 20 mg moxisylyte. Indeed, for each erectile parameter (rigidity, abdominopenile angle, length and circumference of the penis), no statistically significant difference arose between the 4 tests. All patients achieved full rigidity. Neither priapism nor prolonged erection occurred. These results suggest that discreet and easily handled small-sized injection pens, containing little solution, could be conceived for autoinjection therapy.