Pyridoxamine (PM) is one of three natural forms of vitamin B6. It is a critical transient intermediate in catalysis of transamination reactions by vitamin B6-dependent enzymes. In preclinical or clinical trials PM has demonstrated pharmacological potential for treatment of diabetic nephropathy, diabetic retinopathy, and hyperlipidemia, and for use in kidney stone preventive therapies. Although its precise mode of action in vivo is not yet clear, it is likely that at least three mechanisms are at play: inhibition of post-Amadori steps of the Maillard reaction; scavenging of reactive carbonyl compounds; and inhibition of toxic effects of ROS. Pyridoxamine was marketed as a dietary supplement, often as the hydrochloride salt, pyridoxamine dihydrochloride. However, in the United States, the FDA ruled in January 2009 that pyridoxamine must be regulated as a pharmaceutical drug because it is the active ingredient in Pyridorin, a drug designed to prevent the progression of diabetic nephropathy.