The invention provides a formulation to be administered as dry powder forinhalation suitable for efficacious delivery of low-dosage strength activeingredients to the low respiratory tract of patients. In particular, theinvention provides a formulation comprising microparticles constituted ofmicroparticles of a low-dosage strength active ingredient and microparticlesof an excipient wherein the MMD of the microparticles is comprised between 2and 15 micron, at least 10% of the microparticles has a mass diameter (MD)higher than 0.5 micron, and the process of preparation thereof.
