Dermal and Transdermal Drug Delivery Systems
Tapash K. Ghosh in Dermal Drug Delivery, 2020
This chapter reviews progress in the development of dermal and transdermal delivery systems. Both dermal and transdermal drug therapy for local and systemic effect require the active agent to be delivered to the site of action. Skin permeation and enhancement technologies, together with delivery systems, have been the regular subject of updates and reviews, as have the differences between diseased and normal stratum corneum. It has been known for some time that permeation across the skin is controlled mainly by the tortuous but continuous intercellular lipid of the stratum corneum. The authors investigated the comparative skin permeation and found that the permeation of desogestrel was significantly greater than that of levonorgestrel. The intercellular lipid lamellae are highly structured, very stable and provide a highly effective barrier to chemical penetration and permeation. While permeation of ondansetron through pig skin from a base gel was low, the addition of isopropyl myristate or camphor improved delivery.
Structure and Function of Human Skin
Marc B. Brown, Adrian C. Williams in The Art and Science of Dermal Formulation Development, 2019
This chapter describes the structure and function of healthy human skin, and considers some skin-related factors that can affect transdermal and topical drug delivery, such as body site, the overlying skin microbiome, and age-related alterations to the membrane. Human skin is a remarkable barrier between the body and the environment, providing protection against ingress of allergens, chemicals, and microorganisms, regulating the loss of water and nutrients from the body and responding to mitigate the effects of ultraviolet (UV) radiation. The anatomy of human skin is complex, but for the purpose of transdermal and topical drug delivery, we can examine its structure and function in four main layers: the innermost subcutaneous fat layer, the overlying dermis, the viable epidermis and the outermost layer of the tissue the stratum corneum . Three main appendages found on the surface of human skin originate in the dermis; the pilosebaceous unit, eccrine glands, and apocrine glands.
Microneedles and Transdermal Transport
Boris Stoeber, Raja K Sivamani, Howard I. Maibach in Microneedling in Clinical Practice, 2020
The rate of micropore closure is another important factor in determining its efficacy as a drug delivery mechanism. A slow closure rate provides adequate time for the drug to diffuse across the tissue. The dermis is the layer of skin underlying the epidermis, measuring 1–2 mm in thickness. It consists of nerves, vasculature, hair follicles, and glandular structures, held in place by a network of elastin and collagen fibers embedded in ground substance, which is the gel-like extracellular matrix that exists in the extracellular spaces. Drug delivery through the skin is often minimally invasive and allows for more frequent administration. It also provides a larger surface area for drug absorption. And finally, transdermal drug delivery bypasses hepatic first-pass metabolism and deactivation through gastric enzymes. The use of microneedles for transdermal delivery of drugs enables circumvention of the thick stratum corneum by creating small conduits in the stratum corneum, allowing deeper penetration of drugs.
The importance of minipigs in dermal safety assessment: an overview
Published in Cutaneous and Ocular Toxicology, 2017
Alain Stricker-Krongrad, Catherine R. Shoemake, Jason Liu, Derek Brocksmith, Guy Bouchard
The use of miniature swine as a non-rodent species in safety assessment has continued to expand for over a decade and their use has become routine, particularly in pharmacology as a model for human integumentary diseases. Translational preclinical swine study data are now favorably compared and contrasted to human data, and miniature swine models provide important information in dermal safety assessment and skin pharmacology. For example, the miniature swine model has been well-accepted for cutaneous absorption and toxicity studies due to swine integument being morphologically and functionally similar to human skin. Subsequently, this model is important to dermal drug development programs, and it is the animal model of choice for assessment of dermal absorption, local tolerance and systemic toxicity following dermal exposures. In conclusion, the miniature swine model has an important role to play in the safety assessment of pharmaceutical products and in multiple aspects of human dermal drug development.
A Structured Observational Method to Assess Dermal Exposure to Manufactured Nanoparticles: DREAM as an Initial Assessment Tool
Published in International Journal of Occupational and Environmental Health, 2010
Birgit Van Duuren-Stuurman, Johannes Pelzer, Carsten Moehlmann, Markus Berges, Delphine Bard, Derrick Wake, Dave Mark, Elzbieta Jankowska, Derk Brouwer
Preliminary results of inventories of exposure scenarios for nanomaterials have indicated possible dermal exposure. Within the NANOSH project focused on occupational safety and health aspects of nanotechnology a shortened version of the observational DeRmal Exposure AssessMent (DREAM) method was used as an initial method to assess dermal exposure. A total of 45 tasks (such as bagging, dumping, and cleaning) involving different manufactured nanoparticles (MNPs) such as carbon nanotubes, fumed silica, and cerium oxide, were observed in industrial and research facilities. In 39 tasks potential dermal exposure (that is, exposure of the skin and clothing) was likely to occur. Exposure resulted from different routes, including direct contact with MNPs as well as the deposition or transfer of MNPs. The survey showed it is both feasible and useful to assess the potential dermal exposure using shortened DREAM questionnaires.
The use of dermal automesh for incidental hernia repair in abdominoplasty: Clinical, biochemical, and radiological results
Published in Journal of Plastic Surgery and Hand Surgery, 2015
Özay Özkaya Mutlu, Onur Egemen, Arzu Akan, Mithat Akan, Mehmet Karahangil, Gaye Filinte, Ergün Bozdağ, Emin Sünbüloğlu, Hülya Kurtul
Abdominal wall hernias are often diagnosed on clinical examination or encountered intraoperatively during an abdominoplasty. The aim of this study is to evaluate the long-term results of the use of dermal automesh for the repair of incidental hernias during abdominoplasty operations, and to perform a comparative analysis of the biomechanical strengths of dermal automesh vs biological tissue graft. Between 2008–2012, dermal automesh was used in 12 patients for hernia repair. After repair of hernia, dermal automesh was applied over the repaired area in an onlay fashion. Postoperative follow-up was performed by physical examination and magnetic resonance imaging (MRI) of the abdominal wall. Biomechanical test was performed with prepared samples from excised abdominal panniculus for tensile strength and yield power. Mean age was 45 years (range = 36–54 years). Total follow-up was 26 (14–52) months. MRI studies showed that there were no hernias or defects of the anterior abdominal wall. The tensile strength of the dermal mesh was measured as 15.9 ± 6.0 Mpa (6.4–24.5), maximum load before yield measured 680 ± 175.2 N (336.0–856.0). In conclusion, dermal automesh is a useful option for surgeons who encounter undiagnosed hernias during abdominoplasties.