Abstract: AimTo prepare insulin powder for inhalation by spray-drying technology, determine the deposition of the insulin powder formulation in vitro and preliminarily investigate hypoglycemic response of the dry powder with/without absorption promoters. MethodsThe depositions of the insulin powder for inhalation were determined by the China Pharmacopoeia 2000 version addenda XH and hypoglycemic effects were evaluated by testing serum glucose with glucose oxidase-peroxidase (GOD-PAP) method. ResultsThe depositions of the spray-dried insulin powder for inhalation were more than 40% under various humidity and their changes were not significant when air flow was no less than 18 L·min^-1. The coadministration of insulin with 8 mmol·L^-1/dose sodium taurocholate ［PA=59.91%, C _nadir=(33±6)%］ and 10 mmol·L^-1/dose sodium deoxycholate ［PA=47.46%, C _nadir=(32±7)%］ induced a significantly greater decline in blood glucose levels, while coadministration with 1% sodium caprylate, 1% sodium dodecyl sulfate, 250 μg/dose lecithin, 10 mmol·L^-1/dose EDTA appeared to have no significant effect (P>0.05). ConclusionInsulin powder for inhalation was relatively stable under various humidity conditions and different flow current. The use of 8 mmol·L^-1/dose sodium taurocholate and 10 mmol·L^-1/dose sodium deoxycholate could be able to potentially improve the bioavailability of insulin by pulmonary route.