The objective of this investigation is to investigate the feasibility of sublingual insulin administration. Insulin solutions formulated with permeation enhancers (HPβCD/poloxamer 188) and their in-vitro and in-vivo performances were evaluated. Thereafter, insulin fast-dissolving film was further developed to have similar properties, upon dissolving the film, of the optimized insulin solution. In-vitro performance was evaluated via effect of HPβCD and/or poloxamer 188 concentration across cellulose acetate membrane and porcine esophagus. In-vivo performance was evaluated via pharmacodynamic and pharmacokinetic profiles of insulin solution administered. Cumulative amounts of insulin permeated at 60 min formulated with HPβCD (5%), poloxamer 188 (0.5%), and their combination were 1.31, 3.23, and 4.99 IU/cm2, respectively, indicating an additive effect of combination of HPβCD and poloxamer 188. Insulin-induced hypoglycemic effect was observed for insulin solutions with combination of HPβCD and poloxamer 188 after sublingual administration to Sprague-Dawley rats. Microscopic evaluation of porcine oesophageal tissue indicates that HPβCD and poloxamer 188 are safe. Furthermore, the cumulative amount permeated across cellulose acetate membrane at 30 min was 1.13 and 1.00 IU/cm2 for insulin solution and fast-dissolving film, respectively, demonstrating to be similar. In conclusion, the use of HPβCD/poloxamer 188 is feasible for the development of sublingual insulin solutions/films.
Keywords: Insulin; fast-dissolving film; hydroxypropyl beta-cyclodextrin; permeation enhancers; poloxamer; sublingual route.