With a promise of ease of drug administration and the potential for a high degree of patient compliance and reduced side effects, there has been increasing interest in the areas of transdermal, topical and follicular drug administration. In this special focus issue we will explore the advances that are being made in these fields.
In a study exploring follicular administration of flutamide for the treatment of androgenic alopecia, Hamishehkar and coworkers formulated the drug into Solid Lipid Nanoparticles (SLNs) using a hot melt homogenization technique. The researchers found a higher skin drug deposition in vitro and greater hair follicle growth in vivo when compared to an alcoholic control solution of the drug. The authors indicated that these promising results could suggest a higher accumulation and contuinuous release of flutamide from the SLNs in the hair follicles. This valuable study offers a ray of hope for the many sufferers of alopecia around the world. Another study, looking at hair follicle permeation by Kumar et al., follows the development of adapalene liposomes. The group hypothesized that by targeting delivery to pilosebaceous units, side effects may be reduced and better patient compliance could be afforded. Adapalene liposomes were prepared by the film hydration method and fully characterized before evaluation of adapalene permeation in pig ear skin and hair follicles. The group used confocal microscopy to confirm drug penetration to the desired target site for acne therapy. A further study for the treatment of acne, in this special focus edition, looked at the fabrication and characterization of a topically applicable gel loaded with nanostructured lipid carriers (NLCs) of adapalene (ADA) and vitamin C. After preparing a suitable formulation, Jain and coworkers performed in vivo studies in testosterone-induced acne in male Wistar rats to look at skin compliance, permeation, bio-distribution, and anti-acne therapeutic potential. The group report improved targeting of the skin epidermal layer and reduced systemic penetration. The co-administration of vitamin C led to an adjunct effect for acne therapy in physiological conditions. In brief, the present results suggest the potential of NLCs as a novel carrier for the dermal delivery of ADA and also the synergistic effect of vitamin C in topical therapeutics.
An original research article by Froelich explores the characteristics of indomethacin (IND) semisolid polymer gels. IND is a poorly water soluble non-steroidal anti-inflammatory drug (NSAID), and one of the desired routes of administration for NSAIDs has been to target directly the site of pain and/or inflammation rather than by a systemic approach that could lead to a greater issue with side effects. The authors describe the critical attributes of a topical formulation by evaluating rheological and textural properties, and how incorporation of IND affects these properties. Another original research article by Rodrigues et al. explores the development of a novel antioxidant cream and its potential to be used as a topical treatment. The study focuses on the repurposing of two byproducts from the food industry: coffee silverskin from the coffee roasting process, as well as a by-product that is high in antioxidants and isoflavones from Medicago sativa. The research shows how a body cream formulation containing the two by-product extracts, compared against a control formulation. Furthermore, by assessment of in vitro cell toxicity and in vivo skin safety, protective effects were also assessed.
A common theme throughout the studies highlighted in this special focus edition is the issue of drug translocation across the skin. In a study aimed at the evaluation of a pediatric pain relief transdermal patch, Ravula et al. investigated the diffusion of hydrocodone bitartrate, codeine, and acetaminophen across porcine ear skin and dermatomed human skin epidermis for 24 hours. The authors were able to demonstrate the rate and extent of diffusion of the drugs and confirm that the addition of oleic acid (a known absorption enhancer) enhanced the solubility and permeation of the drugs evaluated. Another approach to mitigate the issues associated with translocation of pharmaceutically active compounds has been the application of microneedles. In an article by Chen et al. the use of dissolving microneedles is investigated for the intradermal delivery of interferon-α-2b. The group describes in vitro release tests showing efficiency of 49.2%, and go on to describe a complete pharmacokinetic analysis. The study indicates that this transdermal delivery approach has the potential to provide a useful alternative to a highly invasive intramuscular administration.
All in all this is a valuable collection of articles for those interested in this field, and we on the editorial board would like to thank the authors for their high quality contributions.