Novel Drug Delivery Systems (Part 2)

Nasopulmonary drug delivery has gained a lot of interest as a convenient, reliable, and promising technique for systemic drug administration. It is especially used for molecules that can only be delivered intravenously and are inefficient when taken orally. This is due to the high vascularization seen above the upper nasal cavity and alveolar region of the pulmonary system, wide surface area, avoidance of first-pass metabolism, gut wall metabolism, and/or destruction in the gastrointestinal tract. Numerous therapeutic compounds may be supplied intranasally for topical or systemic administration. Presently, the nose-to-brain administration route offers targeted delivery. Several further advantages are expected to emerge via the pulmonary route to achieve systemic effects and treat lung disorders. Barriers that prevent absorption through the nasal and pulmonary pathways must be overcome to achieve these therapeutic benefits. Numerous drug delivery devices are being researched for nasal and pulmonary administration of liquid, semisolid, and solid formulations to deliver the medications quickly and/or efficiently to the target area. They are especially suitable for the administration of biotechnological products like proteins, peptides, hormones, and vaccines, as well as poorly soluble drugs, to improve bioavailability. Pulmonary drug delivery has triggered intense scientific and biomedical interest in recent years, and it has made significant progress in the context of local treatment for lung disorders, owing to improved local targeting and fewer systemic adverse effects with the administration of minute therapeutic levels. The chapter attempts to provide some information regarding the nasopulmonary drug delivery system, including the anatomy of the nasal cavity and respiratory tract, the mechanism of drug absorption, characteristics that are considered during the selection of drugs for the nasopulmonary system, factors that affect nasal and pulmonary drug absorption, techniques to improve absorption, dose calculation specifically for intranasal delivery, formulation of dosage forms according to requirement, novel drug formulations, recent improvements of the nasal and pulmonary delivery systems, and some of the patents and commercially also available formulations. The impact of COVID-19 and intranasal vaccine development is discussed in this chapter. 

Significant breakthroughs in transdermal delivery of drugs have occurred in recent years owing to new technology and strategies used for transporting drug across the skin. Transdermal drug delivery systems (TDDS) provide many benefits, such as the avoidance of hepatic clearance, ease of application, better patient acceptance, and regulated release of medication; yet, patients and physicians still face numerous challenges. Due to the skin's excellent barrier function and lipophilic nature, one of the main obstacles for TDDS is the restricted amount of drug placement, specifically for drugs with molecular weights > 500 Da. Many pharmacological molecules, including high molecular weight pharmaceuticals, have been the subject of much research, especially in relation to biotechnologically manufactured medications delivered using TDDS. This chapter covers the principles of transdermal drug delivery systems, including their types, components, evaluation, lab and large-scale manufacture. This chapter also emphasizes on new technologies that have improved skin permeability and the regulatory considerations for transdermal formulation.

Ophthalmologists and drug delivery scientists face considerable challenges in the realm of ocular drug delivery, primarily attributable to the intricate structural and barrier complexities inherent in the eye. The presence of various barriers, including the multilayered cornea, sclera, conjunctival blood flow, and tear dilution, imposes limitations on the efficacy of drug delivery, affecting both the anterior and posterior segments of the eye. To overcome these challenges, researchers have explored diverse delivery systems to enhance drug delivery and treatment outcomes. Among the conventional ocular drug delivery systems, the ophthalmic solution or eye drop stands out as a widely utilized and consumer-preferred option. Existing market formulations include emulsions, suspensions, and ointments. Concurrently, scientists have been investigating innovative formulations such as liposomes, solid lipid nanoparticles, nanostructure lipid carriers, nanoparticles, hydrogel, and contact Lenses as potential future treatments, offering advancements in ocular drug delivery and serving as alternatives to traditional delivery methods.

This book chapter aims to provide a comprehensive summary of both conventional and novel topical formulations for ocular drug delivery. By examining the current landscape of ocular drug delivery systems, this chapter seeks to contribute valuable insights into the ongoing efforts to improve treatment efficacy and patient outcomes in the challenging domain of ocular therapeutics.

Nanotechnology is a new platform through which the delivery of therapeutics takes place using nanoformulation to overcome the pharmacokinetics challenges of the drug. This chapter presents an overview of nanotechnology-based delivery systems such as liposomes, polymeric nanoparticles, solid lipid nanoparticles (SLNs), nanostructured lipid carriers (NLCs), and lipid polymer hybrid nanoparticles. The potential advantages of the use of a nanotechnology-based delivery system over the conventional drug delivery system are highlighted. The rationale for the development of a nanotechnology-based delivery system is discussed in detail. The aspects of various characterization studies of nanoparticles and their effect on performance behavior are discussed. The potential applications of nanotechnologybased delivery systems and nonparticulate drug delivery systems, such as oral, dermal, ocular, and parenteral, are currently being explored.

Miniaturized systems, known as implantable drug delivery systems, are used to administer medicinal medicines to specific sites within the body. They are made of biocompatible substances that enclose the drug payload and control its kinetics of release, enabling sustained delivery. These systems provide a number of benefits by avoiding the drawbacks of oral drugs and conventional injectable techniques, including increased bioavailability, fewer systemic side effects, and improved patient adherence. The key characteristics and elements of implanted drug delivery systems, such as the drug reservoir, release mechanism, and sensing capabilities, are highlighted in this chapter. It explores several implant design techniques that allow for exact control of drug release rates, including micropumps, microelectromechanical systems, and biodegradable polymers. Potential uses for implantable drug delivery systems (IDDSs) include the management of chronic pain, hormone replacement therapy, the management of cardiovascular diseases, and cancer. The challenges and considerations to be taken into account when developing IDDSs, such as biocompatibility, device integration, and long-term dependability, are also covered in this chapter. Furthermore, it explores ongoing studies aiming at enhancing remote monitoring capabilities, drug loading capacity, and device performance. By enabling accurate and localized administration, IDDSs have the potential to revolutionize the field of targeted treatments. These technologies have promising potential for enhancing the patient’s quality of life, lowering healthcare costs, and improving treatment outcomes.

The importance of controlled-release injections in drug delivery, including the recent technological developments in injectable emulsions, liposomes, and nanosuspensions for parenteral drug delivery, is discussed in four major sections in the current chapter. The 1st section delves into the application of these systems for poorly soluble drugs, proteins/peptides, vaccines, and gene therapeutics, highlighting their potential to overcome challenges associated with bioavailability, stability, and targeted delivery. In the 2n d section, injectable emulsions are discussed as a formulation to overcome key formulation tasks such as solubilization of poorly water-soluble drugs as well as drugs susceptible to hydrolysis. The utility of injectable nanoemulsions exhibits enhanced stability and tissue penetration, while multiple emulsions show promise despite inherent complexity. Microemulsions offer a thermodynamically stable option for parenteral drug delivery. Tactics for improving poorly water-soluble drug delivery, sustained release, and targeted delivery using injectable emulsions are discussed. It also offers an overview of the physical and chemical properties and approaches used for the preparation of emulsion formulations. Emulsion stability assessments and characterization parameters essential for formulation development are also highlighted. An overview of the physicochemical characteristics of liposomes and the process by which drug-containing liposomes are formed is given in the 3rd part. It reviews a number of liposome preparation techniques, along with the number of drug loading and encapsulating methods. Examples of marketed and experimental products are provided while discussing the usage of injectable liposomes as a medication delivery vehicle. In the 4th section, nanosuspensions as a promising tactic for the formulation using the poorly water-soluble and poorly bioavailable drug candidates is discussed. The section navigates the complexities of manufacturing, emphasizing the importance of particle size distribution for stability. It explores diverse nanoparticle manufacturing techniques for formulating injectable nanosuspensions. Focusing on injectable nanosuspensions, it involves the application in controlled release, highlighting the significance of excipients, particle size, syringeability, and sterility for successful formulation.