A process for preparing a powder formulation for inhalation for use in a dry powder inhaler, said powder comprising: a carrier comprising: (a) 80 to 95 percent by weight, based on the total weight of said carrier, of coarse particles of a physiologically acceptable excipient having a mean particle size of at least 175 μm; and (b) 19.6 to 4.9 percent by weight, based on the total weight of said carrier, of micronized particles of a physiologically acceptable excipient, and 0.1 to 0.4 percent by weight, based on the total weight of said carrier, of a salt of a fatty acid; and micronized particles of an anti-muscarinic drug, a long-acting β 2 -agonist (LABA), and optionally, an inhaled corticosteroid, as active ingredients, said process comprising: (i) mixing all of said coarse particles of a physiologically acceptable excipient, all of said salt of a fatty acid, a first portion of said micronized particles of a physiologically acceptable excipient, all of said micronized particles of said long-acting β 2 -agonist, said anti-muscarinic drug, and, optionally, said inhaled corticosteroid in a vessel of a shaker mixer at a speed of rotation not lower than 16 r.p.m. for a time of not less than 60 minutes, to obtain a first mixture; and (ii) adding the remaining part of said micronized particles of a physiologically acceptable excipient to said first mixture, to obtain a second mixture, and mixing said second mixture at a speed of rotation not lower than 16 rpm for a time of at least 120 minutes, wherein the long-acting β 2 -agonist is selected from the group consisting of formoterol, salmeterol, indacaterol, olodaterol, and vilanterol; the anti-muscarinic drug is selected from the group consisting of glycopyrronium bromide or chloride, tiotropium bromide, umeclidinium bromide, and aclidinium bromide; the inhaled corticosteroid is selected from the group consisting of beclomethasone dipropionate and its monohydrate form, budesonide, fluticasone propionate, fluticasone furoate, and mometasone furoate. a carrier comprising: (a) 80 to 95 percent by weight, based on the total weight of said carrier, of coarse particles of a physiologically acceptable excipient having a mean particle size of at least 175 μm; and (b) 19.6 to 4.9 percent by weight, based on the total weight of said carrier, of micronized particles of a physiologically acceptable excipient, and 0.1 to 0.4 percent by weight, based on the total weight of said carrier, of a salt of a fatty acid; and (a) 80 to 95 percent by weight, based on the total weight of said carrier, of coarse particles of a physiologically acceptable excipient having a mean particle size of at least 175 μm; and (b) 19.6 to 4.9 percent by weight, based on the total weight of said carrier, of micronized particles of a physiologically acceptable excipient, and 0.1 to 0.4 percent by weight, based on the total weight of said carrier, of a salt of a fatty acid; and micronized particles of an anti-muscarinic drug, a long-acting β 2 -agonist (LABA), and optionally, an inhaled corticosteroid, as active ingredients, said process comprising: (i) mixing all of said coarse particles of a physiologically acceptable excipient, all of said salt of a fatty acid, a first portion of said micronized particles of a physiologically acceptable excipient, all of said micronized particles of said long-acting β 2 -agonist, said anti-muscarinic drug, and, optionally, said inhaled corticosteroid in a vessel of a shaker mixer at a speed of rotation not lower than 16 r.p.m. for a time of not less than 60 minutes, to obtain a first mixture; and (ii) adding the remaining part of said micronized particles of a physiologically acceptable excipient to said first mixture, to obtain a second mixture, and mixing said second mixture at a speed of rotation not lower than 16 rpm for a time of at least 120 minutes, (i) mixing all of said coarse particles of a physiologically acceptable excipient, all of said salt of a fatty acid, a first portion of said micronized particles of a physiologically acceptable excipient, all of said micronized particles of said long-acting β 2 -agonist, said anti-muscarinic drug, and, optionally, said inhaled corticosteroid in a vessel of a shaker mixer at a speed of rotation not lower than 16 r.p.m. for a time of not less than 60 minutes, to obtain a first mixture; and (ii) adding the remaining part of said micronized particles of a physiologically acceptable excipient to said first mixture, to obtain a second mixture, and mixing said second mixture at a speed of rotation not lower than 16 rpm for a time of at least 120 minutes,