Dry-Powder Inhalers
Hans Bisgaard, Chris O’Callaghan, Gerald C. Smaldone in Drug Delivery to the Lung, 2001
When the inhalation starts, the powder is contained in the dosing disk, the capsule, or the blister. The inhalation initiates the dispersion of particles when enough space is created between the particles for them to pass around and over each other in the direction of the flow. The flow of the particles is not predictable due to the nonuniform shape of dry powders and the various adhesive and cohesive forces. When more air is drawn through the powder, it starts to fluidize. Fluidization is defined as the mobilization of a bulk powder by air. In gas-assisted fluidization, gas (air) is actually forced through the powder and fluidization occurs when a low-pressure field is established close to the powder. A pressure difference between the air contained in the powder and the motion of air passing over the powder is developed and the powder is fluidized. Shear force fluidization occurs when a gas stream is passed over a powder source and the particles on the surface experience reduced interparticulate forces. Collisions with other particles may occur and the particles bounce, resulting in incipient fluidization. Vibrational fluidization occurs, for example, when the powder is shaken and falls through the air by gravitational forces.
Fluid Bed Processing
Dilip M. Parikh in Handbook of Pharmaceutical Granulation Technology, 2021
Fluidization is the unit operation by which fine solids are transformed into a fluid-like state through contact with a gas. At certain gas velocities, the gas will support the particles, giving them freedom of mobility without entrainment. Such a fluidized bed resembles a vigorously boiling fluid, with solid particles undergoing extremely turbulent motion, which increases with gas velocity. The smooth fluidization of gas-solid particles is the result of an equilibrium between the hydrodynamic, gravitational, and interparticle forces.
Development of taste-masking microcapsules containing azithromycin by fluid bed coating for powder for suspension and in vivo evaluation
Published in Journal of Microencapsulation, 2023
Pham-Thi-Phuong Dung, Thanh-Dat Trinh, Quoc-Hoai Nguyen, Huu-Manh Nguyen, Ngoc-Chien Nguyen, Ngoc-Bao Tran, Cao-Son Tran, Thi-Hong-Ngoc Nguyen, Nguyen-Thach Tung
There are three types of fluid bed systems based on the site of nozzle: top-spray, bottom-spray, and tangential-spray (Saurabh and Garima 2010). In such fluid bed systems, the basic concept of fluidisation relies on the compensation of the gravity force experienced by the particles and an upward moving air flow, which ensures complete fluidisation of the particles. Typical fluidised bed apparatus can efficiently process particles from 100 mm to a few millimetres (Saurabh and Garima 2010). However, for very small particles, other forces such as electrostatic forces start to play a major role in the movement of the particles in the fluidisation chamber and prevent adequate fluidisation (Gouin 2004). Therefore, it is necessary to control the size of core particles loaded in coating chamber and key process parameters such as air flow, inlet temperature, spraying pressure, and spraying rate. In the first stage of this study, cores of bitter taste microcapsules were prepared by binding drug particles to get size of upper 125 µm. In the second stage, taste-masking layers were covered onto the core’s surface by fluid bed coating method.
Airway geometry, airway flow, and particle measurement methods: implications on pulmonary drug delivery
Published in Expert Opinion on Drug Delivery, 2018
A. Kourmatzis, S. Cheng, H.-K. Chan
High-speed photography [140,141] or Mie Scattering [127,142] is another avenue for analyzing inhaler performance. Shur et al. [141] used high-speed photography in conjunction with impactor measurements to classify aerosol characteristics. The high-speed photographs implied that lactose processed using a different amount of shear exhibited different fluidization properties; however, the images were not well resolved. An increase in cohesion resulted in a different fluidization mechanism (plug type flow for high cohesion and erosive flow for low cohesion). Similarly to the work of Shur et al. [141], work by a different group [143] also used high-speed imaging to classify fluidization mechanisms and powder evacuation characteristics from simple optically accessible geometries exposed to more realistic pressure–time profiles [143]. Erosion and fracture mechanisms of fluidization were identified similarly to [141]. High-speed imaging has also been employed to measure powder deagglomeration under the influence of electric charge [144], with the authors concluding that particles with rough surfaces formed stronger agglomerates and rebounded from a wall subsequent to impaction [144].
Microfluidics in drug delivery: review of methods and applications
Published in Pharmaceutical Development and Technology, 2023
Mutasem Rawas-Qalaji, Roberta Cagliani, Noor Al-hashimi, Rahma Al-Dabbagh, Amena Al-Dabbagh, Zahid Hussain
The micro-fluidization technique depends on microfluidic platforms. It is involved high-pressure streams of aqueous phase and oil phase that moves toward to the interaction chamber or an impingement area, thus causing a high shearing action and fine emulsions within the submicron size (Lu and Park 2013). Micro-fluidization technology produces very fine particle sizes with low heat production (Ostertag et al. 2012; Salvia-Trujillo et al. 2015). Nano-emulsions carriers enhanced numerous properties of drug molecules, such as stability, solubility, bio-accessibility, and bioavailability (Shakeel et al. 2012; Choi C.H. et al. 2013; Tang et al. 2013; Tan et al. 2015; Hussain et al. 2016; De Paula et al. 2017).
Related Knowledge Centers
- Acrylonitrile
- Calcination
- Catalysis
- Gasoline
- Monomer
- Petroleum
- Vinyl Chloride
- Liquefaction
- Fluid Catalytic Cracking
- Coke