Physicochemical factors governing the performance of nedocromil sodium as a dry powder aerosol

Particle Engineering for Pulmonary Drug Delivery

With the rapidly growing popularity and sophistication of inhalation therapy, there is an increasing demand for tailor-made inhalable drug particles capable of affording the most efficient delivery to the lungs and the most optimal therapeutic outcomes. To cope with this formulation demand, a wide variety of novel particle technologies have emerged over the past decade. The present review is intended to provide a critical account of the current goals and technologies of particle engineering for the development of pulmonary drug delivery systems. These technologies cover traditional micronization and powder blending, controlled solvent crystallization, spray drying, spray freeze drying, particle formation from liquid dispersion systems, supercritical fluid processing and particle coating. The merits and limitations of these technologies are discussed with reference to their applications to specific drug and/or excipient materials. The regulatory requirements applicable to particulate inhalation products are also reviewed briefly.

The use of colloid probe microscopy to predict aerosolization performance in dry powder inhalers: AFM and in vitro correlation

The atomic force microscope (AFM) colloid probe technique was utilized to measure cohesion forces (separation energy) between three drug systems as a function of relative humidity (RH). The subsequent data was correlated with in vitro aerosolization data collected over the same RH range. Three drug-only systems were chosen for study; salbutamol sulphate (SS), triamcinolone acetonide (TAA), and di-sodium cromoglycate (DSCG). Analysis of the AFM and in vitro data suggested good correlations, with the separation energy being related inversely to the aerosolization performance (measured as fine particle fraction, FPF(LD)). In addition, the relationship between, cohesion, RH, and aerosolization performance was drug specific. For example, an increase in RH between 15% and 75% resulted in increased cohesion and decreased FPF(LD) for SS and DSCG. In comparison, for TAA, a decrease in cohesion and increased FPF(LD) was observed when RH was increased (15-75%). Linear regression analysis comparing AFM with in vitro data indicated R(2) values > 0.80, for all data sets, suggesting the AFM could be used to indicate in vitro aerosolization performance.

Solid-state analysis of the active pharmaceutical ingredient in drug products

The solid form of a drug substance is important when developing a new chemical entity. The crystalline form used in development is significant based on possible manufacturability, solubility, bioavailability and stability differences between the solid forms. Regulatory issues require that the form present in a solid dosage form or liquids containing undissolved drug substance be identified. Drug product samples can be analyzed by a variety of techniques to determine the crystal form present or changes that occur during the manufacture of a drug product. The form present will affect development, regulatory and intellectual property issues.

The formulation of powder inhalation systems containing a high mass of nedocromil sodium trihydrate

Nedocromil sodium trihydrate is not amenable to conventional methods of dry powder inhaler formulation, including the preparation of coarse carrier systems and aggregation of the pure drug powder. It is considered that the in vitro aerosol performance of such systems is governed by the cohesive drug-drug interactions. Therefore, alternative powder formulation strategies (novel to nedocromil sodium) were developed. By decreasing the particle size of the lactose carrier, the deaggregation and subsequent fine particle drug deposition were significantly improved. Further improvements were made by selecting and then optimizing high-shear mixing procedures. It was concluded, based on these findings and supportive microscopic studies (low-temperature and environmental scanning electron microscopy together with energy-dispersive X-ray analysis), that the FPL are producing their functional effects by intercalating within the drug self-agglomerates and physically disrupting the cohesive drug-drug interactions. The use of a smaller-sized lactose fraction in conjunction with a blending procedure capable of optimally disrupting the drug self-agglomerates allowed maximal intercalation of the excipient material within the drug self-agglomerates. The adhesive drug-FPL interactions are considered to be weak compared with the cohesive drug-drug particle interactions, cohesive interactions that would normally govern the aerosol performance of powder systems containing a high mass of nedocromil sodium trihydrate.