Istamet is an advanced medicine in better diabetes management and a patented medicine by MSD pharmaceuticals and they supply it to Sun pharmaceuticals . This medicine is basically having imported active chemical Sitagliptin which is not manufactured in India so there is no substitute for it. This group of medicines is known as Gliptins - Sitagliptin, Vildagliptin, saxagliptin, alogliptin and linagliptin. All are exclusive and little pricy medicines but they are very good medicines as compare to others. So if you can afford it then please continue these. If it is a problem on household budget than for sure you have to change these. Consult your doctor for other medicines.