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Abstract
Purpose: A low-viscosity formulation for pulmonary delivery of rh-insulin as model peptide drugs was developed using a solution of sodium hyaluronate. Method: The effects of different concentrations and pH values of low-viscosity solutions of hyaluronate on the pulmonary absorption of rh-insulin were examined after intratracheal administration in rats. The permeation of fluorescein isothiocyanate (FITC)–dextran(molecular weight 4300; FD-4) and insulin through excised rat trachea in vitro were also examined. Results: The hyaluronate (2140 kDa) solutions (0.1% and 0.2%w/v) at pH 7.0 significantly enhanced the pharmacological availability (PAB) of insulin compared to the aqueous solution of insulin at pH 7.0. The absorptionenhancing effect at a concentration of 0.1% w/v hyaluronate was greater than that at a concentration of 0.2% w/v hyaluronate. Furthermore, the greatest absorptionenhancing effect was obtained, regardless of the molecular weight of hyaluronate, when the concentration of hyaluronate was adjusted to 0.47 µM. Absorption-enhancing effects were consistent with the effect of a 0.1% w/v hyaluronate preparation at pH 4.0 and 7.0 on the permeation of FITC-dextran and insulin through excised rat trachea in vitro. Conclusion: Low-viscosity hyaluronate preparation was shown to be a useful vehicle for pulmonary delivery of peptide drugs.