Development Of Dry Powder Inhalers Research Articles

Air classifier technology (ACT) in dry powder inhalation: Part 1. Introduction of a novel force distribution concept (FDC) explaining the performance of a basic air classifier on adhesive mixtures

Air classifier technology (ACT) is introduced as part of formulation integrated dry powder inhaler development (FIDPI) to optimise the de-agglomeration of inhalation powders. Carrier retention and de-agglomeration results obtained with a basic classifier concept are discussed. The theoretical cut-off diameter for lactose of the classifier used, is between 35 and 15 μm for flow rates ranging from 20 to 70 l/min. Carrier retention of narrow size fractions is higher than 80% for flow rates between 30 and 60 l/min, inhalation times up to 6 s and classifier payloads between 0 and 30 mg. The de-agglomeration efficiency for adhesive mixtures, derived from carrier residue (CR) measurement, increases both with increasing flow rate and inhalation time. At 30 l/min, 60% fine particle detachment can be obtained within 3 s circulation time, whereas at 60 l/min only 0.5 s is necessary to release more than 70%. More detailed information of the change of detachment rate within the first 0.5 s of inhalation is obtained from laser diffraction analysis (LDA) of the aerosol cloud. The experimental results can be explained with a novel force distribution concept (FDC) which is introduced to better understand the complex effects of mixing and inhalation parameters on the size distributions of adhesion and removal forces and their relevance to the de-agglomeration in the classifier.

Pulmonary disposition of budesonide from liposomal dry powder inhaler.

The Purpose of this study was to establish the use of a developed dry powder inhaler of budesonide liposomes in pulmonary drug delivery. Budesonide liposomes composed of egg phosphatidyl choline (EPC) and cholesterol were prepared using a lipid-film hydration technique. The liposomal dispersion was freeze dried and formulated to a dry powder inhaler. The entrapped drug values (91.79% to 78.99%) of freeze dried liposomes were estimated in prepared batches after purification from the free drug by centrifugation of the rehydrated vesicles. In vitro drug retention was evaluated using methanolic phosphate buffer saline and bronchoalveolar lavage, following incubation at 37 degrees C. All batches were found to retain more than 63.54% of budesonide within liposomes at the end of 24 h. Rehydrated budesonide liposomes or nonencapsulated budesonide was delivered to rat lungs by intratracheal administration. The pulmonary drug disposition was assessed by simultaneous monitoring of drug levels in the bronchoalveolar lavage and lung tissue. After intratracheal administration, cumulative drug levels in the lung tissue indicated that the targeting factor was at least 1.66 times higher in liposomes. The maximal drug concentration in the lung homogenate for the liposomal dry powder inhaler was 36.64 micrograms as compared to 78.56 micrograms with the plain drug. Similarly, the time for maximum drug concentration in the lung homogenate for the liposomal dry powder inhaler was 9-12 h as compared to 3 h for that of the plain drug. Hence, the use of a developed liposomal budesonide dry powder inhaler was found to provide desired drug levels in the lungs for a prolonged period of time, which is expected to enhance the therapeutic index of the drug and probably reduce the dose and cost of therapy as well.

In Vitro Testing of Dry Powder Inhalers

There is increasing focus on the development of dry powder inhalers (DPIs) for the delivery of therapeutic entities to the lungs. In vitro testing of metered-dose inhalers (MDIs) has evolved through the years and general tests and methods have been published through USP general chapter <601>, monographs, and guidelines issued by the FDA. In contrast, very few guidelines have been established for the testing of dry powder inhaler systems. In fact, these systems may prove to be more difficult to propose general tests for because they are based on different principles leading to a greater diversity in the number of types of devices and formulations in comparison to the MDIs. To form absolute standards at this stage will be difficult and this paper will present a comparison of the in vitro test methods of MDIs to some of the DPIs that are commercially available and suggests some guidelines to follow.