Evaluation of inhaled recombinant human insulin dry powders: pharmacokinetics, pharmacodynamics and 14-day inhalation

Objectives The present study was designed to assess the pharmacokinetic and pharmacodynamic performance of inhaled recombinant human insulin (rh-insulin) dry powders together with their safety profiles after 14-day inhalation. Methods In the pharmacokinetic and pharmacodynamic study, pulmonary surfactant (PS)-loaded and phospholipid hexadecanol tyloxapol (PHT)-loaded rh-insulin dry powders were intratracheally administered to male rats at the dose of 20 U/kg. Novolin R was used as control. Serum glucose and rh-insulin concentrations were determined by glucose oxidase method and human rh-insulin CLIA kit, respectively. For the safety study, rats were exposed to rh-insulin dry powders or air for 14-day by nose-only inhalation chambers. Bronchoalveolar lavage and histopathology examinations were performed after inhalation. Key findings There were no significant differences in the major pharmacokinetic and pharmacodynamic parameters between PS-loaded and PHT-loaded rh-insulin dry powders. The relative bioavailabilities and pharmacodynamic availabilities were 39.9%, 25.6% for PS-loaded dry powders and 30.1%, 23% for PHT-loaded dry powders, respectively. Total protein was the only injury marker that was significantly altered. Histopathology examinations showed the ranking of irritations (from slight to severe) were PHT-loaded rh-insulin, negative air control and PS-loaded rh-insulin. Conclusions Both PS- and PHT-loaded rh-insulin dry powders were able to deliver rh-insulin systemically with appropriate pharmacokinetic, pharmacodynamic and safety profiles.