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, C₁₂H₁₁ClN₂O₅S·C₁₃H₁₈N₄O₃, (I), a 1:1 cocrystal hydrate, C₁₂H₁₁ClN₂O₅S·C₁₃H₁₈N₄O₃·H₂O, (II), and a 1:1 cocrystal acetone solvate, C₁₂H₁₁ClN₂O₅S·C₁₃H₁₈N₄O₃·C₂H₆O, (III). These structures exhibit the presence of a rarely encountered synthon with the graph set R₂²(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.