Meloxicam hydrochloride

Abstract

The title salt, C14H14N3O4S2 +·Cl− [systematic name: 2-(4-hydroxy-2-methyl-1,1-dioxo-1,2-benzothiazine-3-amido)-5-methyl-1,3-thiazol-3-ium chloride] is the hydrochloride derivative of meloxicam, a drug used to treat pain and inflammation in rheumatic disorders and osteoarthritis. Although its molecular structure is similar to that previously reported for the hydrobromide analogue, both salts are not isomorphous. Different crystal structures originate from a conformational modification, arising from a degree of rotational freedom for the thiazolium ring in the cations. By taking as a reference the conformation of meloxicam, the thiazolium ring is twisted by 10.96 and −16.70° in the hydrochloride and hydrobromide salts, while the 1,2-benzothiazine core is a rigid scaffold. This behaviour could explain why meloxicam is a polymorphous compound.