The transdermal route as an alternative for the delivery of drugs for neurodegenerative diseases
Creators: name: Ameen, Dina
Publisher: name: No Publisher Supplied
Year: 2020

description: The transdermal route is an attractive alternative for drug delivery with several advantages including avoidance of gastrointestinal side effects/metabolism and hepatic first-pass effect, constant drug plasma level, being non-invasive, acting as a visual reminder of drug administration, and improved adherence to treatment. The latter is important for the successful management of neurodegenerative diseases, due to their chronic progressive nature requiring prolonged treatment. Despite the advantages, skin is a tough barrier to drug absorption and not many drugs can passively diffuse through the skin into the blood in amounts sufficient to exert a therapeutic effect. The objective of this research was to explore the feasibility and develop transdermal drug delivery systems of drugs for Alzheimer’s disease (AD) and multiple sclerosis (MS). In this work, we investigated the development of a transdermal drug delivery system containing galantamine, an oral drug for AD, in a drug-in-adhesive type of system. Different pressure sensitive adhesives, penetration enhancers, and drug loadings were tested to optimize the drug delivery system through permeation studies using Franz diffusion cells with human cadaver skin, and release and rheological studies. The optimized formulation had a flux enhancement ratio of 2.7-fold and was predicted to achieve a therapeutic plasma level using a 20 cm² patch. The work also investigated the feasibility of transdermal delivery of dimethyl fumarate (DMF), an oral MS drug, by studying the effect of different penetration enhancers at varying concentrations on DMF permeation using vertical Franz diffusion cells and human cadaver skin. The most effective penetration enhancer was found to be 5% cineole with a 5.3-fold increase in enhancement ratio suggesting that DMF is a potential candidate for transdermal drug delivery. Additionally, the feasibility of transdermal co-delivery of DMF and nicotine as a potential treatment for AD was investigated through studying the effect of pH and nicotine form (free base vs. salt) on the permeability of both drugs using human cadaver skin and vertical Franz diffusion cells. The results suggested the possibility of interplay between pH, and ion-pair formation influencing the permeation of DMF if combined with an ionizable molecule (nicotine). Finally, the formulation of DMF in nanostructured lipid carriers (NLCs) was explored through investigating several methods of preparation and compositions and their effects on drug loading and entrapment efficiency. The study involved measuring particle size and distribution, NLCs morphology, drug release and permeation enhancement effect of NLC formulation. Microemulsion method was shown to be successful in producing DMF NLCs with acceptable characteristics and good penetration properties. In conclusion, chemical penetration enhancers and formulation optimization provide feasible approaches to develop transdermal drug delivery systems of the studied drugs for the treatment of AD and MS.