INS and diabetes mellitus: Thus, after a brief summary of IN drug delivery, we will review the potential IN use of insulin, iron chelator deferoxamine (DFX), phosphodiesterase-3 (PDE3) inhibitor cilostazol, endothelin (ET) receptor antagonists, and brain derived neurotrophic factor (BDNF) for improvement of microvascular function and vasoneuronal health in diabetes.