Particles in pharmaceuticals

The study of fine particles in pharmaceutical applications involves a number of different techniques. Micromeritic investigations involve surface areas, particle sizes and their distributions, the nature of solid surfaces, and particle shapes [4]. Scientists working in this field realize that a number of techniques are necessary to fully investigate a system and that an interdisciplinary approach is essential. This ability to correlate data from different techniques allows a more thorough understanding of the system, process, or problem being investigated. 

During extended storage, the particles in (pharmaceutical) suspensions often form agglomerates that can be no longer destroyed by shaking the preparation. This is of particular concern in, for example, eye drops. The problem can be avoided by controlled flocculation of the solids. After the addition of an electrolyte, the fine particles aggregate to loose floes that can be easily redispersed by shaking the dispenser prior to application. 

You will find many of these processing techniques applied to particles in pharmaceuticals, cosmetics, pigments, paints, etc. 

S. Bouhallab and T. Croguennec), the use of DNA/polycation complexes for gene delivery and protection (A. Bertin), and the potential of sizable and shapable nanosized PEC particles in pharmaceutical applications such as controlled drug release (M. Miiller). 

Bosch deals with the role of fine particles in pharmaceutical and therapeutic applications, with special emphasis on the size of the dispersed bioactive materials. The latter can be controlled by mechanical means or by precipitation processes. 

Since latex dispersion application properties are related to the surface properties of the latex particles, there is a need for surface characterization of the particles at large. Historically, these types of systems have been applied as model colloids (Hearn et al, 1981) and therefore required well-characterized surfaces but as the sophistication of new coatings increase, the latex particle surfaces become more important from an industrial perspective. In addition to these applications the utilization of latex particles in pharmaceutical and biomedical applications has also contributed to the development of new surface characterization methods. The surface engineering, that is, variations in size, surface charge and surface hydrophobicity, of latex particles as colloidal carriers has been demonstrated to provide opportunities for the site-specific delivery of drugs (Ilium Davis, 1982). Surface... 

Pharmaceutical powder aerosols have more stringent requirements placed upon the formulation regarding moisture, particle size, and the valve. For metered-dose inhalers, the dispensed product must be deflvered as a spray having a relatively small (3—6 -lm) particle size so that the particles can be deposited at the proper site in the respiratory system. On the other hand, topical powders must be formulated to minimize the number of particles in the 3—6-p.m range because of the adverse effects on the body if these materials are accidently inhaled. 

Mineral fillers are used for light-colored compounds. Talc has a small particle size and is a semireinforcing filler. It reduces air permeabihty and has htde effect on cure systems. Calcined clay is used for halobutyl stoppers in pharmaceutical appHcations. Nonreinforcing fillers, such as calcium carbonate and titanium dioxide, have large particle sizes and are added to reduce cost and viscosity. Hydrated siUcas give dry, stiff compounds, and their acidity reduces cure rate hence, their content should be minimized. 

The tower in which CO2 is stripped out must run into a break-pressure tank with subsequent re-pumping. It will load the water with any dust, and living organisms or other particles in the atmosphere, which leads to trouble in dirty environments or in pharmaceutical works. 

Stokes law is rigorously applicable only for the ideal situation in which uniform and perfectly spherical particles in a very dilute suspension settle without turbulence, interparticle collisions, and without che-mical/physical attraction or affinity for the dispersion medium [79]. Obviously, the equation does not apply precisely to common pharmaceutical suspensions in which the above-mentioned assumptions are most often not completely fulfilled. However, the basic concept of the equation does provide a valid indication of the many important factors controlling the rate of particle sedimentation and, therefore, a guideline for possible adjustments that can be made to a suspension formulation. 

The determination of the zeta potential of particles in a disperse system provides useful information concerning the sign and magnitude of the charge and its effect on the stability of the system (see Sec. II.B) [56, 206 208], It can be of value in the development of pharmaceutical suspensions, particularly if the... 

The slip correction factors are important for particles smaller than 1 pm in diameter, which is rarely the case for pharmaceutical aerosols. Slip correction is required for the Stokes equation to remain predictive of particle behavior for these small particles. Therefore, assuming the absence of shape effects for particles in the Stokes regime of flow, Eq. (1) collapses into the following expression ... 

A variety of techniques are available for sizing particles of pharmaceutical interest. The goal of this chapter is to provide an overview of common techniques currently in use for sizing of powders, and to illustrate their applications. The discussion will focus on techniques used to characterize powders above one micron (jxm) however, it should be emphasized that in some cases the same methods may also be applicable to submicron particles. 

Although short columns with standard particle sizes have found many practical applications in pharmaceutical analysis, the compromised separation efficiency prohibits their use in situations... 

The mineral particles and ash that remain after the ignition of a sample as described above may be important to calculate and report. The mineral and ash are known as the residue. In pharmaceutical... 

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