Advanced Pharmacy

In this chapter, we focus on solutions. In the introduction, general and descriptive aspects are defined, such as the classification of solutions and the addition of solids. Considering the properties of these systems, we focus on definitions related to colligative properties, and on the use of this property for the adjustment of isotonic solutions considering the selective capacity of the membranes, differentiation of tonicity and osmolarity. We also introduce the calculations necessary for the preparation of isotonic solutions with blood plasma, using the mass and volume adjustment method. The solutions require different methods of expressing their concentration, and in order to develop this point, we present the different forms of expression, with extensive detail on one of the variables, i.e., normality, very important in the formulation of parenteral solutions. Since the preparation of solutions is an important aspect, we detail the existing interactions between the solute and the solvent, specify the thermodynamic aspects that condition the solubility of the solute in the solvent, and develop variables such as polar interactions, capacities to accept or give Hydrogen bridge junctions and the energy requirement to generate space within the solvent, giving a rational look at the process of improving the capacity of the solvent to contain the solute. The dissolution rate is another variable developed through simple equations, which make an analysis of the factors that modify it, such as agitation, temperature, particle size, and diffusion coefficient. We also describe variables such as the pH and the dielectric constant of the solvent to modify solubility. 

A relevant area of research in the preformulation phase for the development of new dosages is active pharmaceutical ingredient (API)-excipient compatibility. The possibilities of chemical and physical interaction of API and the excipients may affect how efficient and effective it is, while displaying an impact on the nature, stability and availability of API. The most common signs of deterioration of an API are changes in the color, taste, odor, polymorphic form, or crystallization (pharmaceutical incompatibility). These changes arise from chemical reactions with the excipient, leading to degradation of the API. The active components are usually more stable than solid dosage forms, and although testing the compatibility of API-excipients is essential, no protocol has yet been accepted to evaluate their interactions. Fourier Transform Infrared Spectroscopy (FT-IR), Differential Scanning Calorimetry (DSC), Isothermal Stress Testing-High Performance Liquid Chromatography (IST-HPLC), Hot Stage Microscopy (HSM), Scanning Electron Microscopy (SEM), Solid state Nuclear Magnetic Resonance Spectroscopy (ssNMR) and Power X-ray Diffraction (PXRD) are commonly used as screening techniques for assessing the compatibility of an active pharmaceutical ingredient (API) with some currently employed excipients. The potential physical and chemical interactions between drugs and excipients can affect the chemical nature, the stability and bioavailability of drugs and, consequently, their therapeutic efficacy and safety. Once the solid-state reactions of a pharmaceutical system are understood, the necessary steps can be taken to avoid reactivity and improve the stability of drug substances and products. In this chapter, we summarize the techniques to investigate the compatibility between APIs and excipients.

The application of QSAR/QSPR techniques and computer-aided modelling are considered valuable tools to initiate the search for new drugs, and nowadays, these are being intensively used for this purpose. Trustworthy models can provide insight into the structural characteristics that may influence the drug inhibitory activity, drastically improving the success and the pace of the development of more effective drugs with weaker secondary effects. The present book chapter revises and comments on different recent QSAR/QSPR applications conducted in medicinal chemistry field in the last five years (2016-2020), developed on various interesting biological activities and physicochemical properties of drug compounds.

Although many sulfur-containing garlic compounds exhibit antioxidant activity, little is known about the molecular mechanisms through which these compounds react with reactive oxygen species. For this reason, in this chapter, we present a summary of various papers in which, the scavenging of hydrogen peroxide and hydroxyl radical by garlic compounds allyl methyl disulfide, allyl methyl sulfide, and diallyl sulfide is analyzed from a theoretical-quantum outlook. Different computational methods and methodologies were analyzed. The DFT functional B3LYP, CAM-B3LYP, BKM, M05-2X, and M06-2X and even other methods such as Gaussian-n (G3MP2B3) were also evaluated. A broad series of basis sets were used from the simple 6-31G(d) to the extended triple-zeta 6-311++G(3df,2p). The thermodynamic and kinetic aspects of different proposed reactions were explored. Epoxidation, sulfonation, and hydrogenation were some of the processes raised as possible reaction pathways. Reaction mechanisms were proposed for each pathway, and different methods used to obtain the TS structure (TS Berny, QST2, and QST3) were compared. The kinetic and the rate constants were obtained through the Intrinsic Reaction Coordinate calculations. Gas and aqueous phases were mostly utilized in our papers; however, we included and studied the behavior of the systems in non-polar environments in our last publication. 

Enzymes are proteins that efficiently catalyze chemical reactions of specific substrates; they are highly specific for one reaction or a class of reactions, based on the structure of their active sites. This chapter presents the classification according to the nature of the reactions where enzymes are involved as biocatalysts and shows examples of biocatalyzed chemical processes. Kinetic aspects are discussed, and the relevance of the kinetic parameters is highlighted. Inhibitors of enzyme-mediated reactions are also described and classified; their kinetic implications are revealed; besides, examples of enzyme inhibition, examples of pharmacological drug-inhibition are presented. The roles of enzyme cofactors and cosubstrates are described taking examples of biological systems. Enzymes are also used in bioremediation processes and examples are mentioned. Enzyme production strategies developed to enable industrial application are presented, taking lactase as a model example; enzyme preparation, purification, recovery, and stabilization are the key steps in their utilization. Nowadays, with the development of genomics and proteomics, it is possible to access new enzyme activities as well as manipulate, design and improve new and traditional enzyme activities. Biocatalysis is a multidisciplinary area of science that is gaining increasing interest both from a scientific point of view and for its growing industrial applications due to its high specificity in the conversion of substrates into specific products, the reduced volume of waste generated and the non-aggressive operating conditions. Specifically, the enzymes’ use in pharmacological drugs synthesis is remarkably interesting, since they allow to improve both the performance and the stereoselectivity of the active principles.

Fungal infections represent an increasing threat to a growing number of immune- and medically compromised patients. Fungi, like humans, are eukaryotic organisms and there are a limited number of selective targets that can be exploited for antifungal drug development. This has also resulted in a very restricted number of antifungal drugs that are clinically available for the treatment of superficial and invasive fungal infections at the present time. Moreover, the utility of available antifungals is limited by toxicity, drug interactions and the emergence of resistance, which contribute to high morbidity and mortality rates. These limitations have created a demand for the development of new antifungals, particularly those with novel mechanisms of action. The 1990s can be considered the “golden era” of antifungal drug development with multiple big pharmaceutical companies actively engaged in the discovery and development of novel antifungals. However, this has largely become stagnant since then, and it has been two decades since the newest class of antifungal agents (the echinocandins) reached the market. Overall, there are currently few classes of FDA-approved antifungal agents clinically used in the treatment of fungal infections. In this chapter, we reviewed antifungal drugs and summarized their mechanisms of action, pharmacological profiles, and susceptibility to specific fungi. Approved antimycotics inhibit nucleic acid and microtubule synthesis, membrane ergosterol synthesis and cell wall polymers’ synthesis, or sequestrate ergosterol. The experimental antifungal drugs in clinical trials are also reviewed. We report sphingolipids and protein biosynthesis inhibitors, which represent the most promising emerging antifungal therapies.

Sulfated polysaccharides have always attracted much attention in food, cosmetic and pharmaceutical industries. These polysaccharides can be obtained from natural sources such as seaweeds (agarans, carrageenans, fucoidans, mannans and ulvans), or animal tissues (glucosaminoglycans). In the last few years, several neutral or cationic polysaccharides have been sulfated by chemical methods and anionic or amphoteric derivatives were obtained, respectively, for drug delivery and other biomedical applications. An important characteristic of sulfated polysaccharides in this field is that they can associate with cationic drugs generating polyelectrolyte-drug complexes, or with cationic polymers to form interpolyelectrolyte complexes, with hydrogel properties that expand even more their applications. The aims of this chapter are to present the structural characteristics of these polysaccharides, to describe the methods of sulfation applied and to review extensively and discuss developments in their use or their role in interpolyelectrolyte complexes in drug delivery platforms. A variety of pharmaceutical dosage forms which were developed and administered by multiple routes (oral, transdermal, ophthalmic, and pulmonary, among others) to treat diverse pathologies were considered. Different IPECs were formed employing these sulfated polysaccharides as the anionic component. The most widely investigated is κ-carrageenan. Chitosan is usually employed as a cationic polyelectrolyte, with a variety of sulfated polysaccharides, besides the applications of chemically sulfated chitosan. Although chemical sulfation is often carried out in neutral polysaccharides and, to a less extent, in cationic ones, examples of oversulfation of naturally sulfated fucoidan have been found which improve its drug binding capacity and biological properties.

Medicinal herbs have been in use for the management of human health, for prevention. as well as for the cure of human diseases since ancient civilizations. In recent times, the use of herbal drugs has increased in both developed and developing countries, because of the large chemical, pharmacological, and clinical knowledge of plant drugs and their derivatives, the development of new analytical methods for quality control, the development of new forms of preparation and administration of plant drugs and their derivatives and finally the relatively wide therapeutic margins with less frequent adverse effects. However, naturals are not a synonym for innocuous as many adverse effects can occur. In this regard, there are different levels of perceptions about the safety of medicinal herbs, varying from “completely safe” to “completely harmful”, although there is also a clear idea about its side effects depending on factors such as dosage, characteristics of the plant material and consumer-related factors. Because of this, medicinal plants need to be studied and effective and innocuous doses must be established. Nowadays, immunomodulatory drugs have gained a main role principally as a consequence of COVID-19 produced by the SARS-CoV-2 virus. Some South American plants frequently used in Argentine folk medicine such as Larrea divaricata and Ilex paraguariensis and others used all over the world like Tilia spp. and Coffeea Arabica are known to exert immune-enhancing effects. In this review, we discussed some reports about the immunological effect of the mentioned plants and their majority compounds, focusing on their efficacy and safety.

Microbial biofilms are communities of sessile cells with a three-dimensional (3D) extracellular polymeric substance (EPS). The EPS consists of exopolysaccharides, nucleic acids (eDNA and eRNA), proteins, lipids, and other biomolecules, that they produce and are irreversibly attached to living or non-living surfaces. This is the most frequent growth mode of microorganisms in nature. The biofilm formation consists of several steps, starting with attachment to a surface and the formation of microcolonies. Subsequently, in the maturation step, three-dimensional structures are formed and end the life cycle of biofilms with the dispersal or detachment of the cells. This type of growth has been reported to be more resistant to antimicrobial treatment and immune response than its planktonic (free-living) counterparts. Several intrinsic resistance factors including the interaction between antimicrobial and biofilm matrix components, reduced growth rates, persister cells presence, increased production of oxidative stress, and antagonist and degradation mechanisms may be active in some parts of the biofilms have been described. Extrinsic factors such as increased horizontal genes transmission conferring antimicrobial resistance have been described contributing to the biofilm antimicrobial resistance. Due to the heterogeneous nature of biofilms, it is likely that multiple mechanisms of biofilm antimicrobial resistance are useful in order to explain biofilm survival in a number of cases, being the result of an intricate mixture of intrinsic and extrinsic factors. The understanding of the nature of biofilm development and drug tolerance are great challenges for the use of conventional antimicrobial agents and indicate the need for multi-targeted or combinatorial therapies.

New Psychoactive Substances (NPS), also known as design drugs, are developed by modification of the chemical structure of the initially prohibited substances. The idea behind this strategy is to create alternatives for consumption and to evade national and international control measures applied to controlled substances, bypassing the legislative prohibition. In this context, the emergence of NPS has raised questions about the analytical methods that can be applied to identify and to characterize these substances in different scenarios, including biological fluids (serum/plasma, whole blood, oral fluid, and urine). Because biological fluids are complex matrixes, a sample preparation step is required to remove undesired endogenous matrix components and to isolate and pre-concentrate the analytes before chromatographic analysis. Different extraction or sample preparation techniques such as liquid-liquid extraction, solid phase extraction, dispersive liquid-liquid microextraction, and microextraction by packed sorbent can be used prior to chromatographic analysis (gas chromatography, mass spectrometry, or liquid chromatography mass spectrometry). All these techniques involve many factors that must be optimized so that the analytical method can detect NPS in biological samples. Tools like design of experiments (DoE) and Response Surface Methodology (RSM) can contribute to the study and optimization of the variables involved in these analytical techniques. This book chapter shows how experimental design tools (full factorial design, fractional factorial design, Plackett-Burman design, Box-Behnken design, central composite design) and response surface methodology can aid the development of analytical methods for the analysis of drugs of abuse in biological fluids.

This chapter describes the different difficulties encountered when studying a new polymer by GPC or SEC. This technique is known as liquid chromatography in which a soluble polymer is eluted through a porous gel filling a column. The different molecular weights are separated following their hydrodynamic volumes compared with the pore diameters. It appeared in the sixties firstly in an aqueous medium. The main factors playing a role in the elution through the porous support are examined. Especially, the SEC behaviour of water-soluble polymers is discussed introducing the behaviour in aqueous medium where H bonds and hydrophobic interactions are important. Examples of dextrans and neutral oligosaccharides, rich in -OH groups are discussed showing that weak adsorption increases the elution volumes when eluted in water. Other important interactions concern the electrostatic interactions causing exclusion from the gels and changes in the polyelectrolyte conformation. Elution with monovalent electrolytes (NaNO3 or NaOAc) around 0.1M is recommended. SEC of charged oligosaccharides, hyaluronan, pectins and chitosan are briefly described. Fortunately, new equipment appeared progressively and especially in 1983 the multiangle laser light scattering (MALLS) was introduced, which is probably the most useful detector to associate with the differential refractometer. In that case, Mw is obtained independently of the elution volume as soon as there are no aggregates and good solubility of the polymer tested in the solvent selected. To conclude, it is necessary to insist on the quality of the polymeric solution avoiding the presence of aggregates which may be identified by dynamic light scattering (DLS). In their presence, even after filtration on 0.2 µm pore membrane, the SLS overestimates the Mw.

Intrinsic viscosity is the most economical and used measure in the determination of polymers and biopolymers used as excipients in the pharmaceutical industry. The most used methods in the measurement of intrinsic viscosity are Huggins, Kraemer, Schulze-Blashke and Martin, the first being used as a standard and reference for the others. There are also Simple Point methods such as Solomon Ciuta and others that help in this regard. In this chapter, we will focus on those methods best known and applied in intrinsic viscosity measurements. In the measurement of intrinsic viscosity in dilute solutions of polymers, experimental methods such as Huggins, Martin, Kraemer and Shulze-Blashke are particularly useful. In dilute concentrations, graphical methods such as those of Fuoss, Fidors, and Tanglertpaibul and Rao can also be used without major errors. Although there are many more methods these can be more difficult and impractical in their calculations and graphs. The methods furthest from experimental practicality are those that depend on other methods and constants, such as Budtov's and Baker´s. As for the simple point methods, the simplest and most used is that of Solomon-Ciuta, the rest have similar or better results. As for the proposed methods, the most prominent and with the least error is Square, the rest being affordable but with a somewhat higher margin of error

Analytical chemistry determinations are not exempted from generating environmental contamination. A variety of strategies are now being proposed to reduce the impact on the environment caused by the different stages of the analytical process. These strategies can focus on the different stages of the analysis, ranging from sample collection and preparation to the acquisition and processing of analytical signals. Sample preparation constitutes a basic and crucial stage in the success of any analytical method and extraction is one of the most chosen techniques. Extractions often involve the use of a large amount of harmful solvents that may damage the health of the operator and the environment, into which these solvents are disposed of, often without treatment. Therefore, new techniques have been applied in order to reduce the impact of this procedure, also focusing on lowering the costs and complexity, always taking into account the quality of the procedures. Current trends in green analytical chemistry are directed towards simplification, miniaturization, and automation, also involving the use of solvent-free, environmentally friendly procedures and, at the same time, maintaining acceptable extraction efficiencies in a short time. In this chapter, the fundamentals and technological advances in green extraction systems will be presented. Through representative examples of different compounds in different matrices, the advantages and limitations of different procedures will be presented, including ultrasound-assisted extraction, pressurized solvent extraction, microwave-assisted extraction, single drop liquid-liquid extraction, headspace extraction, dispersive liquid-liquid microextraction, hollow-fiber liquid-phase microextraction, micro-solid phase extraction, stir-bar sorptive extraction and stir-cake sorptive extraction