Multicomponent pharmaceutical cocrystals: furosemide and pentoxifylline.

The combination of the active pharmaceutical ingredients furosemide [4-chloro-2-(furan-2-ylmethylamino)-5-sulfamoylbenzoic acid] and pentoxifylline [3,7-dimethyl-1-(5-oxohexyl)-3,7-dihydro-1H-purine-2,6-dione] produces a 1:1 cocrystal, C(12)H(11)ClN(2)O(5)S·C(13)H(18)N(4)O(3), (I), a 1:1 cocrystal hydrate, C(12)H(11)ClN(2)O(5)S·C(13)H(18)N(4)O(3)·H(2)O, (II), and a 1:1 cocrystal acetone solvate, C(12)H(11)ClN(2)O(5)S·C(13)H(18)N(4)O(3)·C(2)H(6)O, (III). These structures exhibit the presence of a rarely encountered synthon with the graph set R(2)(2)(7). All potential hydrogen-bond donors of furosemide participate in hydrogen-bond formation in (I)-(III). However, only two hydrogen-bond acceptors of furosemide are active in (I) and (II), and only one is active in (III). Four hydrogen-bond acceptors of pentoxifylline are active in (II), three in (I) and two in (III). These observations are in good agreement with the calculated packing indexes of 69.5, 69.6 and 68.8% for (II), (I) and (III), respectively.