A new solvate of furosemide with dimethylacetamide.

The loop diuretic furosemide is used widely in the treatment of congestive heart failure and edema, and is practically insoluble in water. The physicochemical and pharmacokinetic properties of drugs can be modified by preparing the drug in an appropriate solid-state form. A new solvate of furosemide with dimethylacetamide (DMA) {systematic name: 4-chloro-2-[(furan-2-yl)methylamino]-5-sulfamoylbenzoic acid N,N-dimethylacetamide disolvate}, C12H11ClN2O5S·2C4H9NO, (I), is reported. The channeled structure formed on slow crystallization contains DMA solvent molecules in its channels. This structure adds to the evidence of varied conformations observed across all known structures, so supporting the idea that this flexible molecule has conformational lability. The current structure also differs from those of other previously known furosemide solvates in the number of solvent molecules per furosemide molecule, viz. 2:1 instead of 1:1. Desolvation of (I) gives the most stable form of furosemide, i.e. Form I.