The present invention is directed to nanostructured (nanoparticulated) Candesartan or its pharmaceutically acceptable ester, preferable Candesartan Cilexetil, or co-crystal compositions, process for the preparation thereof and pharmaceutical compositions containing them. The nanoparticles of Candesartan or its pharmaceutically acceptable ester, preferable Candesartan Cilexetil, or co-crystal according to the invention have an average particle size of less than about 500 nm. Candesartan Cilexetil is a prodrug, is hydrolyzed to Candesartan during absorption from the gastrointestinal tract. Candesartan is a selective AT1 subtype angiotensin II receptor antagonist.
