Abstract
Administration of active pharmaceutical ingredients (APIs) through the skin, by means of topical drug delivery systems, is an advanced therapeutic approach. As the skin is the largest organ of the human body, primarily acting as a natural protective barrier against permeation of xenobiotics, specific strategies to overcome this barrier are needed. Liposomes are nanometric-sized delivery systems composed of phospholipids, which are key components of cell membranes, making liposomes well tolerated and devoid of toxicity. As their lipid compositions are similar to those of the skin, liposomes are used as topical, dermal, and transdermal delivery systems. However, permeation of the first generation of liposomes through the skin posed some limitations; thus, a second generation of liposomes has emerged, overcoming permeability problems. Various mechanisms of permeation/penetration of elastic/ultra-deformable liposomes into the skin have been proposed; however, debate continues on their extent/mechanisms of permeation/penetration. In vivo bioavailability of an API administered in the form of ultra-deformable liposomes is similar to the bioavailability achieved when the same API is administered in the form of a solution by subcutaneous or epi-cutaneous injection, which demonstrates their applicability in transdermal drug delivery.
Highlights
The skin is the largest organ of the human body, weighing up to 16% of total body weight, and consisting of a complex structure of several strata that form a barrier between the body and the external environment [1,2]
As the stratum corneum is the main barrier for transdermal mass transport through the skin, the therapeutic plasma levels of active pharmaceutical ingredients (APIs) are compromised; distinct approaches have been developed to improve the transdermal absorption of APIs, which include vesicles, such as liposomes [8], niosomes [9], and ethosomes [10], which can be combined with invasive techniques e.g., microneedles [11,12], iontophoresis [13], electroporation [14], and ultrasounds [15]
The results showed that the liposome formulation significantly increased the amount of drug that was placed on the surface of the stratum corneum and that permeated the skin, compared to the marketed product
Summary
The skin is the largest organ of the human body, weighing up to 16% of total body weight, and consisting of a complex structure of several strata that form a barrier between the body and the external environment [1,2]. As the stratum corneum is the main barrier for transdermal mass transport through the skin, the therapeutic plasma levels of APIs are compromised; distinct approaches have been developed to improve the transdermal absorption of APIs, which include vesicles, such as liposomes [8], niosomes [9], and ethosomes [10], which can be combined with invasive techniques e.g., microneedles [11,12], iontophoresis [13], electroporation [14], and ultrasounds [15] The application of the latter onto the skin is, recommended as a fast and reversible process, so that no toxic effects on epidermal and dermal cells are seen [5]. Schematic representation of an ultra-deformable liposomal system to administer APIs (on the right)
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