Preface

Abstract

The research in therapeutic systems has increased quickly with the development of new materials and new mathematical approaches, and further application of physicochemical tools. Moreover, the great development of biotechnology and the understanding of physiological mechanisms have enabled the possibility of designing dosage forms that are each more specialized. This is increasing the number of strategies that can be applied to develop systems with enhanced properties in relationship to modifying and controlling the delivery of active agents.This book, "Strategies to Modify the Drug Release from Pharmaceutical Systems," emerged with the aim of providing a comprehensive reference on drug delivery and strategies to modify the drug release from dosage forms, covering all main topics in the field. From the earliest dosage forms to modern drug delivery systems has come great development and growth of acquired knowledge. Thus, this textbook addresses principles, systems, applications, and advances in the field. It is principally a textbook and a reference source of strategies to modify the drug release. Moreover, the characterization, mathematical and physicochemical models, applications, and systems are discussed.Some students and researchers may consider this book an excellent starting point to study the field, while others may find it a source of principles, systems, applications, and advances in the field of drug delivery systems addressed in the same book. It is designed for individuals of diverse backgrounds who are interested in the field of drug delivery. The mathematical and physicochemical principles are highlighted and related with the strategies aiming to discuss and understand the drug release and its possible modifications. It is a book involving the principles, systems, mechanisms, and the state of the art in just one volume.The book is divided into six chapters, according to its sixfold purpose: (I) General considerations, (II) Modification of drug release, (III) Classification of therapeutic systems for drug delivery, (IV) Main mechanisms to control the drug release, (V) Mathematical and physicochemical models of drug release, and (VI) Drug delivery systems. Each chapter is devoted to a specific group of concepts and definitions, and contains contributions from established or emerging researchers around the world who have been working in this field.Through many years of studying and lecturing on this theme for undergraduate and graduate students, I have observed the need to have in one book the discussion about the main strategies to modify the drug delivery and the fundamentals about the theme. I sincerely hope that this textbook will help pharmaceutical students and scientists to understand the fundamentals and main points involving the strategies to modify the drug release. The knowledge about drug delivery systems will enable a more specialized understanding, research and development of drug delivery systems, contributing to patient compliance and enhanced therapy. viii Preface

An Inhalable Powder Formulation Based on Micro- and Nanoparticles Containing 5-Fluorouracil for the Treatment of Metastatic Melanoma

“…The mathematical model applied to these results, which presented the coefficient value “ n ” estimated by the Power Law model, indicates that the anomalous release mechanism found for the 5FU-MS formulation occurs as a result of the combined and simultaneous action of solvent diffusion and swelling of the polymeric matrix processes (0.43 < n < 0.85), prolonging the time of drug release. On the other hand, the value of n > 0.85 observed for the 5FU-NS formulation suggests the super-case II release kinetics in which the solvent diffusion rate through the matrix is increased compared with the relaxation of the polymer (chondroitin), favoring the erosion process of the system [ 56 ]. The lower free fraction of drug in the medium is of great relevance given that its short half-life and toxic side effects are a significant disadvantage in the conventional form of administration.…”

Fabrication and Characterization of Electrospun Membranes Based on “Poly(ε-caprolactone)”, “Poly(3-hydroxybutyrate)” and Their Blend for Tunable Drug Delivery of Curcumin

“…The release kinetics of curcumin from the electrospun membranes were carried out in a pseudo-biologic fluid (PBS/EtOH 70:30 v / v ). The drug release profiles were analyzed and fitted by applying the statistical Weibull model [ 70 , 71 ], expressed by Equation (7) [ 72 ]: m/m 0 = 1 − exp((−1/A) × (t − T) b ) where m is the amount of drug dissolved as a function of time t, m 0 is total released amount of drug, T parameter represents the latency time resulting from the release process, the scale factor A accounts for the time dependence, and b parameter is related to the drug release mechanism [ 73 ]. Moreover, the release phenomenon could be considered the combination of two drug transport phenomena: a diffusion-controlled phase and a relaxation-controlled phase.…”

Degradable Poly(ethylene oxide)-Like Plasma Polymer Films Used for the Controlled Release of Nisin

“…The acquired experimental data were analyzed by applying the power law equation (Equation (2)). The equation is commonly considered to be valid for M t /M 0 < 0.6 [ 27 ], but, due to the limited number of data points given by the time constraints of the measurements, we included the data points up to M t /M 0 < 0.95. For simplicity, we fixed the kinetics exponent at n = 0.5 as for classical diffusion.…”

“…The release kinetics of nisin before saturation was characterized by the modified Korsmeyer-Peppas model [ 26 , 27 ]: where M t and M 0 are the amounts of nisin in the sample at time t and 0, respectively; and K , n , and b are constants characterizing the release rate, kinetics exponent ( n = 0.5 for Fickian diffusion through planar carrier) and initial burst/lag, respectively.…”