Transdermal Drug Delivery Systems: A Review of Conventional and Modern Approaches

Transdermal drug delivery is a method of delivering drugs through the skin into the bloodstream. It is used to provide controlled drug release and can help avoid gastrointestinal degradation and first-pass metabolism. Conventional systems, such as patches, gels and creams, are widely used for the treatment of different diseases. However, drug delivery through the skin is limited by the stratum corneum, which acts as the main barrier to drug penetration. To overcome this limitation, several modern transdermal technologies have been developed. These include microneedles, iontophoresis, sonophoresis, electroporation and nanocarrier-based systems such as liposomes, transfersomes, ethosomes and solid lipid nanoparticles. Smart and wearable devices are also being studied to improve drug delivery and provide better control over drug release. This review discusses the basic principles, types and applications of conventional and modern transdermal drug delivery systems. It also compares these systems based on drug penetration, drug release, safety, manufacturing, cost and clinical use. Conventional systems have established clinical applications, while many advanced technologies are still under research. Challenges related to skin irritation, formulation stability, large-scale manufacturing and regulatory approval need further attention. Future research may help improve the safety and effectiveness of these systems and increase their use in clinical practice.