Priya K. Sharma*
Department of Pharmaceutical Sciences, University of Delhi, India
Received: 02-Sep-2025, Manuscript No. dd- 25-182238; Editor assigned: 04-Sep-2025, PreQC No. dd-25-182238 (PQ); Reviewed: 15-Sep-2025, QC No. dd-25-182238; Revised: 20-Sep-2025, Manuscript No. dd- 25-182238(R); Published: 29-Sep-2025, DOI: 10.4172/dd.9.002.
Citation: Priya K. Sharma, Transdermal Drug Delivery, Microneedles and Drug Permeation. RRJ Drug Deliv. 2025.9.002.
Copyright: © 2025 Priya K. Sharma, this is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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Transdermal drug delivery refers to the administration of therapeutic agents across the skin for systemic effect. It offers important advantages over oral and injectable routes, including avoidance of first-pass metabolism, improved patient compliance, and sustained drug release. However, the skin’s primary function as a protective barrier limits the number of drugs that can be delivered effectively. The outermost layer, the stratum corneum, is highly impermeable to most molecules, particularly large or hydrophilic drugs [1]. To overcome this limitation, advanced technologies such as microneedles have been developed to enhance drug permeation across the skin.
Discussion
Drug permeation through the skin is governed by diffusion, concentration gradient, molecular size, lipophilicity, and the condition of the skin barrier. Conventional transdermal patches are effective mainly for small, lipophilic, and potent drugs, such as nicotine or hormones. Many modern therapeutics, including peptides, proteins, and vaccines, cannot cross the stratum corneum efficiently [2,3]. This challenge has driven interest in physical enhancement techniques, among which microneedles are particularly promising.
Microneedles are microscopic needle-like structures, typically 50–900 µm in length, designed to penetrate the stratum corneum without reaching pain receptors in deeper tissues. They create temporary microchannels in the skin, significantly increasing permeability while minimizing discomfort and risk of infection. Microneedles can be solid, coated, hollow, dissolving, or hydrogel-forming, each designed for specific drug delivery purposes. For example, dissolving microneedles encapsulate drugs within a biodegradable matrix that dissolves after insertion, eliminating sharp waste [4,5].
By bypassing the stratum corneum, microneedles allow both small molecules and macromolecules to enter systemic circulation. This improves bioavailability and enables controlled drug release. In vaccination, microneedles have shown the ability to target immune cells in the skin, potentially enhancing immune responses while simplifying administration. Their ease of use also supports self-administration and improves adherence to long-term therapies.
Despite these advantages, challenges remain. Manufacturing consistency, mechanical strength, drug loading capacity, and large-scale production must be optimized. Regulatory approval and long-term safety data are also necessary for widespread clinical adoption.
Conclusion
Transdermal drug delivery offers a patient-friendly alternative to traditional administration routes but is limited by the skin’s barrier function. Microneedle technology represents a major advancement by safely and effectively enhancing drug permeation. By combining minimal invasiveness with improved delivery of a wide range of therapeutics, microneedles have the potential to expand the scope of transdermal systems. Continued research and development are expected to establish microneedles as a key platform in future drug delivery strategies.
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