Analysis of the influence of relative humidity on the moisture sorption of particles and the aerosolization process in a dry powder inhaler

• Published in: Journal of aerosol science Vol. 39; no. 6; pp. 510 - 524
• Main Authors: Zhu, Kewu, Tan, Reginald B.H., Kiong Ng, Wai, Shen, Shoucang, Zhou, Qi, Heng, Paul W.S.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.06.2008; Elsevier Science
• Subjects: Aerosol; Aerosols; Biological and medical sciences; Chemistry; Colloidal state and disperse state; DPI; Drug delivery; Dry powder inhaler; Exact sciences and technology; General and physical chemistry; Humidity; Inhalation; Medical sciences; Pharmacology. Drug treatments; Surface physical chemistry; Dry powder inhaler; Drug delivery; DPI; Aerosol; Humidity; Inhalation; Relative humidity; Drug; Drug delivery systems; Powder; Particle; Sorption; Adsorption; Aerosols; Inhaler
• ISSN: 0021-8502; 1879-1964
• DOI: 10.1016/j.jaerosci.2008.02.003

The purpose of the present work was to analyze the moisture sorption and distribution of pharmaceutical powders at various relative humidities (RHs), to investigate its impact on the inter-particle adhesion force as well as the performance of drug delivery through a dry powder inhaler (DPI). Moisture sorption isotherms were measured and the moisture distribution was analyzed using the GAB method and the Young–Nelson equations for Inhalac 230 ® , salbutamol sulfate, and the binary mixture. Adhesion force of the mixture decreased with RH initially, and then increased upon further increase in RH. An increase in the fine particle fraction of emitted dose ( FPF em ) with RH at low moisture contents appeared to be the result of a reduction in electrostatic force due to charge dissipation associated with moisture sorption, while a decrease in the FPF em at high moisture contents arose from the liquid bridge force. It appeared that the emission efficiency was significantly affected by the electrostatic force. The results suggested that electrostatic force not only influenced the drug FPF em but the drug emission efficiency as well, while the liquid bridge force mainly affected the aerosol FPF em for the DPI system investigated. The results indicated that the influence of the RH on the performance of DPI drug delivery was through its impact on the fundamental electrostatic and liquid bridge forces depending on the distribution of the adsorbed moisture content.