Cystamine is an organic disulfide

Disulfide bond

In chemistry, a disulfide bond is a covalent bond, usually derived by the coupling of two thiol groups. The linkage is also called an SS-bond or disulfide bridge. The overall connectivity is therefore R-S-S-R. The terminology is widely used in biochemistry...

. It is formed when cystine

Cystine

Cystine is a dimeric amino acid formed by the oxidation of two cysteine residues that covalently link to make a disulfide bond. This organosulfur compound has the formula 2. It is a white solid, and melts at 247-249 °C...

 is heated, the result of decarboxylation

Decarboxylation

Decarboxylation is a chemical reaction that releases carbon dioxide . Usually, decarboxylation refers to a reaction of carboxylic acids, removing a carbon atom from a carbon chain. The reverse process, which is the first chemical step in photosynthesis, is called carbonation, the addition of CO2 to...

. Cystamine is an unstable liquid and is generally handled as the dihydrochloride salt, C₄H₁₂N₂S₂·2HCl, which is stable to 203-214 °C at which point it decomposes. Cystamine is toxic if swallowed or inhaled and potentially harmful by contact.