Solid pharmaceutical substances preparation

It is interesting to note that, although crospovidone is insoluble, it can be used in solid pharmaceutical preparations to improve the dissolution rate of an active substance. That this is not merely the result of a short-term increase in the surface area of the active substance but of the formation of a complex, can be seen in Fig. 80. Simply mixing indomethacin with crospovidone multiplies the dissolution rate of this drug substance during more than two hours. Similar results were obtained with indoprofen [439],propyphenazone [426] and prostaglandin ester [359]. 

The optical microscope is a valuable tool in the laboratory and has numerous applications in most industries. Depending on the type of data that is required to solve a particular problem, optical microscopy can provide information on particle size, particle morphology, color, appearance, birefringence, etc. There are many accessories and techniques for optical microscopy that may be employed for the characterization of the physical properties of materials and the identification of unknowns, etc. Utilization of a hot-stage accessory on the microscope for the characterization of materials, including pharmaceutical solids (drug substances, excipients, formulations, etc.), can be extremely valuable. As with any instrument, there are many experimental conditions and techniques for the hot-stage microscope that may be used to collect different types of data. Often, various microscope objectives, optical filters, ramp rates, immersion media, sample preparation techniques, microchemical tests, fusion methods, etc., can be utilized. 

Pharmaceutical products can be classified as liquid solutions, disperse systems (e.g., emulsions, suspensions), semisolids (e.g., ointments), and solid dosage forms. Liquid solutions are homogeneous mixtures of one or more substances in pharmaceutical liquids. The understanding of the physicochemical properties of liquid solutions and processes to prepare the liquid solutions is an important step in preparing final liquid solution dosage forms. In this chapter, the solutions of gases in liquids, liquids in liquids, and solids in liquids, as well as colligative properties of solutions and their application to pharmacy, are discussed. Disperse systems will be discussed in Chapter 4. 

In contrast to previous paragraph, in this case, coating process can also involve a chemical reaction and this approach can be generally named as microencapsulation. Microencapsulated solid preparations are widely used in pharmaceutical, chemical, and other industries to protect various substances from environmental impact, as well as for extending their action [135]. In the... 

Microencapsulated solid preparations are widely used in pharmaceutical, chemical, and other industries to protect various substances from environmental impact, as well as for extending their action [137], In the pharmaceutical field, in particular, these preparations are mainly used to get controlled release drug kinetics, to minimize side effects, to reduce gastric irritations, and to mask the unpleasant taste of the contained drug [137-142]. Indeed, many different active components are microencapsulated analgesics, antibiotics, antihistamine, cardiovascular agents, iron salts, antipsychot-ics [143], vitamins, peptides [144], proteins [145], antiasthma [140,146], broncodilators, diuretics, anticancerogens, tranquilizers, and antihypertensives [137],... 

Many liquid and semi-liquid pharmaceutical preparations are disperse systems. Disperse systems are defined as systems in which a substance is distributed as particles (discontinuous) into a dispersion medium (continuous). Three types of disperse systems will be discussed which are pharmaceutically relevant colloidal systems, suspensions and emulsions. In both colloidal systems and suspensions, solid particles are dispersed in a liquid. The difference is that in colloidal systems the particles do not settle, while they do in suspensions. This difference is caused by the size of the particles. In colloidal systems, the particles are so small (1 mn - 1 pm) that the Brownian motion (diffusion caused by thermal energy) is stronger than the force of gravity so that they remain suspended in the liquid and do not settle. In suspensions, the particles are larger (>1 pm) and as a consequence the force of gravity is stronger than the Brownian motion which makes them settle (if the density of the particles is larger than that of the dispersion medium). Emulsions consist of non-miscible liquids. Two types of emulsions will be discussed oil drops dispersed in water (oil-in-water emulsion or o/w emulsion) and water drops dispersed in oil (water-in-oil emulsion or w/o emulsion). There are also more complex structures such as w/o/w emulsions and bi-continuous systems. However, these systems will not be discussed. 

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