Alfadex also known as α-cyclodextrin, is used as an inactive ingredient in order to improve the water solubility of the different drugs, e.g. edex: is a sterile, pyrogen-free powder containing alprostadil in an alfadex inclusion complex. After intravenous infusion of radiolabeled α-cyclodextrin to healthy volunteers, the radiolabeled components were rapidly eliminated within 24-hours, urine accounting for 81-83% of radioactivity and feces for 0.1%. There was no evidence of significant accumulation of radiolabeled α-cyclodextrin in the body even after 7 days of repeated intravenous injection. After intracavernous administration in monkeys, radiolabeled α¬ cyclodextrin was rapidly distributed from the injection site with less than 0.1% of the dose remaining in the penis 1 hour after administration. There was no evidence of tissue retention of radiolabeled α-cyclodextrin in monkeys.