Meloxicam hydro­chloride

The title salt, C(14)H(14)N(3)O(4)S(2) (+)·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. [Image: see text]