Abstract: AimTo prepare salcatonin dry powder inhalations (sCT-DPIs) A (mixture of mannitol and L-leucine) and B (mixture of manntiol and lactose) by spray-drying and then to study their main pharmaceutical properties. MethodsDumping rate of sCT-DPIs capsules and deposited fraction of sCT at effective part were determined according to Chinese Pharmacopiea 2000. Particle morphology under different relative humidity (RH) was observed by scanning electronics microphotograph, particle size and its distribution were determined by Malvern Mastersizer and the transition of morphorous state for carriers before and after spray-drying was investigated by differential thermal analysis (DTA) and X-ray powder diffraction (XRPD). ResultsDumping rates of sCT-DPIs A and B capsules were both above 10% and deposited fraction of sCT at effective part was above 90% for both A and B, which were all in agreement with the standard of Chinese Pharmacopiea 2000. Powder particle of sCT-DPIs A was round and existed one by one after keeping one month under RH 0, 23% and 52%, but aggregation can be observed under RH 75%; many particles which were also round agglomerated in sCT-DPIs B even under zero RH; mean particle size of sCT-DPIs A was 1.67 μm, which was much smaller than that of sCT-DPIs B; In sCT-DPIs A particle with empty core which was lighter than the same size particle with concreted core was observed. It was shown by DTA that melted heat of L-leucine in sCT-DPIs composed of mannitol and L-leucine lowered much more than that of L-leucine exisited alone after spray-drying. It was confirmed by XRPD that diffraction intensity of carriers in sCT-DPIs decreased more than that of carriers before spray-drying. ConclusionRound particle can be made when mannitol was added to carriers and ultra low density carriers can be formed when L-leucine was added. It was suggested by SEM that DPIs should be kept under certain RH. Particle size and distribution of sCT-DPIs all accorded with demand of DPIs. Complex spray-drying carriers formed amorphous state easier than single carrier.