Influence of carrier on the performance of dry powder inhalers

The aim of this work is to study carriers which can become alternatives to monohydrate lactose in dry powder inhalers and to consider particle parameters that influence adhesion between drug and carrier in dry powder inhalers. Different forms of mannitol, lactose and maltitol were mixed with either terbutaline sulphate or formoterol fumarate. The blends were submitted to different adhesion tests where drug detachment from the carrier was obtained either through mechanical vibration or by aspiration. Parameters like particle shape, roughness, amorphous content and cristalline form may affect interactions between drug and carrier. In our case, crystallized forms of the carrier offered lower adhesion but better release of the active ingredient than spray-dried forms. The crystallized mannitol produced maximal fine particle dose. The blends of the mannitols and the two active ingredients gave different results. The two techniques used to assess the adhesion of drugs to carrier particles provide complementary information about drug/carrier interactions and detachment. The mechanical sieving allows to assess blend stability and the air-jet sieving makes it possible to determine how easily the drug separates from carrier. For the drugs tested, the results of fine particle doses are in agreement with the Alpine air-jet sieve results. The tests used are helpful for the choice of a new carrier in the field of the development of new carriers for dry powder inhalers.