Pimagedine is a nucleophilic hydrazine. It was shown to inhibit diamine oxidase (histaminase), which catalyzes the oxidative deamination of diamines histamine and putrescine. Pimagedine was also reported to inhibit nitric oxide synthase (NOS) based on its structural similarity to the NOS substrate L-arginine. Although pimagedine affects constitutive NOS (cNOS) isoform, it has been demonstrated to be a relatively selective inhibitor of the inducible NOS (iNOS) isoform. Pimagedine was shown to stabilize S-adenosylmethionine decarboxylase (SAMDC). Pimagedine (aminoguanidine HCl) has been shown to be an effective agent in reducing the severity of the structural and functional alterations associated with experimental diabetic nephropathy. But clinical trial of pimagedine to prevent progression of diabetic nephropathy was terminated early due to safety concerns and apparent lack of efficacy.