Pharmaceutical products physicochemical properties

The number of the constituent phases of a disperse system can be higher than two. Many commercial multiphase pharmaceutical products cannot be categorized easily and should be classified as complex disperse systems. Examples include various types of multiple emulsions and suspensions in which solid particles are dispersed within an emulsion base. These complexities influence the physicochemical properties of the system, which, in turn, determine the overall characteristics of the dosage forms with which the formulators are concerned. 

Looking at the downstream processing of recombinant pharmaceutical proteins from different sources as a whole, there are more common steps than operations addressing expression system-specific problems or requirements. One of the most important common features is that a given end product must meet the same standards and specifications in terms of safety, quality, potency and efficacy, regardless of the production host. Furthermore, the physicochemical properties of such end products should be identical, so that the intrinsic features used for purification (affinity, hy-drophobicity etc.) are the same. Well-established procedures and protocols should therefore be utilized, and should be adapted to the special requirements of the source material only when absolutely necessary. This is particularly true in the case of pharmaceuticals, since the tendency in this field is to stick to established methods... 

Though in competition with other analytical techniques, CE has proven its potential and necessity to be used for the characterization of small-molecule pharmaceuticals. Due to the versatility of the system, CE can be applied for the determination of physicochemical properties, identification, purity and stability analysis, and cleaning verification of the drug substance, its precursors, process chemicals, the drug product, and its excipients. 

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. 

Following the ICH (International Conference on Harmonization of Technical Requirements of Pharmaceuticals for Human Use) definition, an impurity is every separate chemical particle present in the active substance and final pharmaceutical product that is not the active substance or excipient. This includes all optical isomers, products of degradation, and polymorphic forms. The physicochemical properties and biological activity of dmg impurities can be similar or different to those of the active substance. Therefore, they can influence the human body in the same way as the medicinal product or differently [7] and lead to an increase or decrease in dmg activity. 

Biopharmaceutics is the study of the interrelationship of the physicochemical properties of the drug [active pharmaceutical ingredient, (API)] and the drug product (dosage form in which the drug is fabricated) based on the biological performance of the drug (Table 1). 

The medicinal chemistry of vitamins is fundamental not only to the therapeutics of nutritional problems but also to the understanding of the biochemical actions of other medicinal agents that directly or indirectly affect the metabolic functions of vitamins and coenzymes. Accordingly, this chapter includes a brief sununary of the basic biochemislry of vitamins, structure-activity relationships, physicochemical properties and some stability considerations, nutritional and therapeutic applications, and brief characterizations of repre.sentative pharmaceutical products. 

As in the case of chemical or pharmaceutical substances, the results from in vitro toxicity testing of NMs are dependent upon many factors, such as the cell types used, exposure time, dosing regimen, and exposure conditions. However, what makes toxicology of NMs so complex as compared to chemical products is the large number of physicochemical properties that are essential to know for proper toxicity assessment. The toxicity mechanisms are multiple and depend strongly on the characteristics of the studied NMs and the conditions of the test. Several aspects may affect the... 

Specifications for the finished product Two specifications at release and end of shelf-life List general characteristics, specific standards tests and limits for results for the finished product must be provided Analytical test procedures described (physicochemical properties, identity of API) Quantitative determination of active, deviations, purity tests, pharmaceutical tests, colouring antimicrobial or chemical preservatives, results of validation studies, comments on the choice of routine tests and standards provided Copy of pharmacopoeia monograph and verification data Results of batch analysis (inc. date of manufacture, place of manufacture, batch size and use of batch tested) ... 

Numerous methods are required to characterize drug substances and drug products (Chapter 10). Specifications may include description identification assay (of composite sample) tests for organic synthetic process impurities, inorganic impurities, degradation products, residual solvents, and container extractables tests of various physicochemical properties, chiral purity, water content, content uniformity, and antioxidant and antimicrobial preservative content microbial tests dissolution/disintegration tests hardness/friability tests and tests for particle size and polymorphic form. Some of these tests may be precluded, or additional tests may be added as dictated by the chemistry of the pharmaceutical or the dosage form. 

In the preformulation study, the comprehension of physicochemical properties regarding water-solid surface interaction is beneficial to the handling, formulation, and manufacture of the finished products. Data on sorption/de-sorption isotherm, hydration of salts of drug product, water sorption of pharmaceutical excipients, and kinetics of water adsorption or desorption of a substance can be obtained effectively by the dynamic vapor sorption method. The knowledge may be utilized for dosage form design and supports the understanding of the mechanism of action. 

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