Influence of Different Amino Acids on the Aerosolization, Stability and Cytotoxicity of Spray-Dried Cannabidiol Dry Powder for Inhalation

Background: Inhaled delivery of cannabidiol (CBD) through dry powder inhalers is a promising approach for achieving optimal drug concentrations in the lungs. Spray drying is a commonly employed technique to prepare inhalable powders with particle sizes ideally ranging from 1 to 5 µm, for deep lung deposition. However, formulating aerosolizable CBD dry powders remains challenging due to the thermolabile nature of CBD and the cohesive behaviour of micron-sized particles, which affects powder dispersibility, reduces de-agglomeration during inhalation, and causes inefficient lung deposition. These challenges can be overcome by the inclusion of excipients that can stabilize CBD during processing and enhance the dispersion and aerosolization of the powder. Objectives and methods: This study investigates the role of different amino acids (lysine, cysteine, arginine, and phenylalanine) in combination with inulin, a sugar-based excipient, on the in vitro aerosolization performance, stability, and cytotoxicity of inhalable CBD dry powders. Results and conclusion: The prepared CBD dry powders exhibited a size range of 1–5 µm. Amino-acid-free CBD powder showed an irregular and flaky morphology, while in association with amino acids, CBD dry powder showed spherical morphology with a dimpled surface. The ATR-FTIR spectra confirmed no interactions between CBD and amino acids in the dry powder formulations. CBD dry powder formulations containing amino acids demonstrated a better aerosolization profile compared to amino-acid-free CBD powder, with the lysine-containing formulation achieving the highest fine particle fraction (FPF) of 56.6%. Additionally, all the formulations were stable under low and high humidity (<15% RH and 53% RH) conditions for 28 days. Cytotoxicity studies on A549 alveolar basal epithelial cells showed that the amino acids were non-toxic, while the CBD formulations with/without amino acids showed comparable levels of cytotoxicity.