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Open AccessArticle

The Effects of Relative Humidity on the Flowability and Dispersion Performance of Lactose Mixtures

School of Medical Instrument and Food Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China
Freeman Technology Ltd., Tewkesbury GL20 8DN, UK
Deprtment of Chemical & Process Engineering, University of Surrey, Guildford GU2 7XH, UK
Advanced Drug Delivery Group, Faculty of Pharmacy, The University of Sydney, Sydney, NSW 2006, Australia
Author to whom correspondence should be addressed.
Academic Editor: Subbu S. Venkatraman
Materials 2017, 10(6), 592;
Received: 9 April 2017 / Revised: 16 May 2017 / Accepted: 24 May 2017 / Published: 29 May 2017
(This article belongs to the Special Issue Materials for Drug Delivery and Biomedical Consideration)
The flowability and dispersion behavior are two important physicochemical properties of pharmaceutical formulations for dry powder inhalers (DPIs). They are usually affected by the environmental conditions, such as temperature and relative humidity (RH). However, very few studies have been focused on the relationship between the two properties and their dependence on RH during storage. In this research, model pharmaceutical formulations were prepared using mixtures of coarse and fine lactose. The fractions of fines in the mixtures were 0%, 5%, 10%, and 20%, respectively. These blends were stored at four different RH levels, 0%, 30%, 58%, and 85%, for 48 h. The FT4 Powder Rheometer was used to evaluate the powder flowability, and the Malvern Spraytec® laser diffraction system was employed to assess the powder dispersion performance. The results indicated that both the flow and dispersion properties of lactose blends deteriorate after being stored at 85% RH, but improved after being conditioned at 58% RH. The fine particle fractions (FPFs) of the blends with 5% and 10% fine fractions and the as-received coarse lactose decreased when they were conditioned at 30% RH. For the blend with 20% fine fraction, a high RH during storage (i.e., 85% RH) affected the dispersion property, but had a limited influence on its flowability, while, for the coarse lactose powder, the different RH conditions affected its flowability, but not the dispersion results. A strong correlation between the powder flowability and its dispersion performance was found. View Full-Text
Keywords: relative humidity; lactose; dry powder inhalation; flowability; dispersion relative humidity; lactose; dry powder inhalation; flowability; dispersion
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MDPI and ACS Style

Lu, X.-Y.; Chen, L.; Wu, C.-Y.; Chan, H.-K.; Freeman, T. The Effects of Relative Humidity on the Flowability and Dispersion Performance of Lactose Mixtures. Materials 2017, 10, 592.

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