A dry powder inhalable formulation of salvianolic acids for the treatment of pulmonary fibrosis: safety, lung deposition, and pharmacokinetic study

Salvianolic acids (SAL), the main bioactive component extracted from Salvia miltiorrhiza, is a natural product with a reported anti-pulmonary fibrosis (PF) effect. SAL is commonly administrated orally; however, it has a low oral bioavailability (less than 5%). The objective of this work was to develop a new dry powder inhalable formulation intended to facilitate the access of SAL to the target place. We prepared the new SAL powder formulation containing L-arginine and 2% of lecithin using the ball milling technique. L-arginine was used to regulate the strong acidity of the SAL solution, and lecithin was added to disperse the powder and improve the flowability. The resulting powder had a content in salvianolic acid B (SALB, the main active principle of SAL) of 66.67%, a particle size of less than 5 μm and a good flowability. In vivo fluorescence imaging showed that the powder could be successfully aerosolized and delivered to the lung. The acute lung irritation study proved that the presence of L-arginine improved the biocompatibility of the powder. Finally, according to the pharmacokinetic study, the new SAL powder formulation was found to significantly increase drug concentration in the lung and the bioavailability. In conclusion, the new dry powder inhalable formulation of SAL developed in this study could be a strategy to enhance the performance of SAL at the lung level. Graphical abstract.