Collecting the Molecular and Ionization States of Irbesartan in the Solid State

An active pharmaceutical ingredient may exist in different solid forms, which are the products of the variation of molecular conformation and packing order stabilized through different intermolecular interactions. Two special conditions, tautomerism and amphoterism, will make the solid-state landscape more abundant and diverse. Two known polymorphs of irbesartan (IBS) contain molecules in different tautomeric forms, respectively. Here, one cationic salt and one anionic salt of IBS were successfully harvested. The NMR spectra demonstrated clear fingerprint features for these four different molecular and ionization states of IBS. The newly obtained crystalline forms also provide much better dissolution performance.