Co-Delivery of a High Dose of Amphotericin B and Itraconazole by Means of a Dry Powder Inhaler Formulation for the Treatment of Severe Fungal Pulmonary Infections

Abstract

Over the past few decades, there has been a considerable rise in the incidence and prevalence of pulmonary fungal infections, creating a global health problem due to a lack of antifungal therapies specifically designed for pulmonary administration. Amphotericin B (AmB) and itraconazole (ITR) are two antifungal drugs with different mechanisms of action that have been widely employed in antimycotic therapy. In this work, microparticles containing a high dose of AmB and ITR (20, 30, and 40% total antifungal drug loading) were engineered for use in dry powder inhalers (DPIs) with an aim to improve the pharmacological effect, thereby enhancing the existing off-label choices for pulmonary administration. A Design of Experiment (DoE) approach was employed to prepare DPI formulations consisting of AmB-ITR encapsulated within γ-cyclodextrin (γ-CD) alongside functional excipients, such as mannitol and leucine. In vitro deposition indicated a favourable lung deposition pattern characterised by an upper ITR distribution (mass median aerodynamic diameter (MMAD) ~ 6 µm) along with a lower AmB deposition (MMAD ~ 3 µm). This offers significant advantages for treating fungal infections, not only in the lung parenchyma but also in the upper respiratory tract, considering that Aspergillus spp. can cause upper and lower airway disorders. The in vitro deposition profile of ITR and larger MMAD was related to the higher unencapsulated crystalline fraction of the drug, which may be altered using a higher concentration of γ-CD.

Keywords: amphotericin B; aspergillosis; dry powder inhaler; infection; itraconazole; lung deposition.

Figure 1

Pareto charts describing the influence of the seven factors in the Taguchi design: (a) yield; (b) particle size; (c) inhibition halo; (d) encapsulation efficiency; (e) aggregation rate. The orange bar represents a positive effect, while the blue bar represents a negative effect. Key: (1) amount of AmB, (2) amount of ITR, (3) amount of γ-CD, (4) amount of leucine, (5) inlet temperature, (6) gas flow rate, (7) solution feed rate. Bonferroni limit: effects that are above the Bonferroni limit are almost certainly important; t-value limit: effects that are above the t-value limit are possibly important.

Figure 2

Two-dimensional contour plots showing the influence of the total amount of drug, the gas flow rate, and the amount of leucine on yield (a–c), particle size (d), and aggregation ratio (e).

Figure 3

SEM micrographs of F1 (A.1,A.2), F2 (B.1,B.2), and F3 (C.1,C.2) at different magnifications.

Figure 4

Physicochemical characterisation of AmB-ITR-MPs: (a) DSC thermograms showing heat flow; (b) DSC thermograms showing reverse heat flow. Key: F1 (1), F2 (2), F3 (3), AmB raw material (4), ITR melt quench (5), ITR raw material (6).

Figure 5

In vitro deposition of F1, F2, and F3 tested in NGI™ apparatus: (a) percentage of AmB recovered at different stages; (b) cumulative AmB deposition; (c) percentage of ITR recovered at different stages; (d) cumulative ITR deposition. Key: F1 (black), F2 (red), F3 (blue). Statistically significant differences are represented by # (F2 vs. F1 and F3) and * (F3 vs. F1 and F2) (p < 0.05, one-way ANOVA post hoc test).