Rosiglitazone maleate 0.25-hydrate: a pseudopolymorphic form.

The present 0.25-hydrated form of rosiglitazone maleate [systematic name: (+/-)-2-({2-[2,4-dioxo-1,3-thiazolidin-5-ylmethyl)phenoxy]ethyl}methylamino)pyridinium maleate 0.25-hydrate], C(18)H(20)N(3)O(3)S(+) x C(4)H(3)O(4)(-) x 0.25 H(2)O, is a racemate with two independent moieties in the unit cell. Although the cation geometry does not differ substantially from that in the previously reported hydrochloride, the packing is quite different, the main feature being the formation of hydrogen-bonded tetramers, linked head-to-tail into weakly interacting chains.