Toward Application of Microsponges in Transdermal Drug Delivery System

Abstract

Abbreviations: TDDS, transdermal drug delivery system; FDA, food and drug administration; EC, ethyl cellulose; BPO, benzoyl peroxide; SEM, scanning electron microscopy; AUC, area under the curve; EE, entrapment efficiency; DSC, differential scanning calorimetry; MED, minimal erythemal dose; SPF, sun protection factor IntroductionCompared with drug dosage forms for oral and parenteral administration, Transdermal drug delivery system (TDDS) can minimize and avoid some restrictions relating to dosage forms effectively. Due to the conventional delivery systems suffering from certain restrictions like Peak and Valley phenomenon i.e., they show fluctuations in plasma drug concentration and cannot render sustained effect.1 However, the TDDS can meet the requirement to keep relatively stable plasma drug concentration and prolong delivery of drug, in a steady-state profile and minimizes the peak-associated side effects, which thus ensures the level of the drug is effective for treatment on the minimal therapeutic concentration. In general, Transdermal drug delivery system, as a controlled drug delivery system, is exceedingly humanized, commodious and prolong the period of time of release of drug, if need arises (e.g. systemic toxicity) with less pain sensation while administrating drug candidates. Additionally, TDDS permits the permeation of drugs across the skin and into the systemic circulation which avoids the hepatic first-pass effect observed in the course of oral administration and inconvenience of frequent parenteral administration. As a new drug carrier of TDDS, Microsponges are mostly used for topical 4-10 and oral administration. 11-15 For other topical delivery systems, the traditional delivery systems are required of frequent dosing to keep relatively stable local concentrations of effective constituent for therapeutic effectiveness because of low effectiveness.Thus to avoid this defect it is indispensable to design a new drug delivery system to prolong the residual time of drug in the epidermis or the dermis, while reduce its penetration into the body. For this reason, as a porous polymeric microsphere, Microsponges can fulfill such aims uniquely.4 Microsponges are porous, polymeric microspheres (Figure 1) which are invariably used for topical delivery system; 4-5,7-10 its inside are full of lacunas and its particle size is 5~300μm in diameter. AbstractTransdermal drug delivery system (TDDS) is a dosage form designed to deliver drug through skin by topical route of administration to the systemic circulation or for local treatment. As a new type of dosage form, TDDS has a number of special merits, but inevitably at the same time it possess some distinct disadvantages, such as low permeability and the drug mostly enter the systemic vascular. Microsponges are a kind of micro-sized and polyporous particles which can entrap effective constituents, and are biologically safe. And Microsponges also exhibit distinctive advantage at the aspect of drug release. The TDDS can enhance drug stability, decrease side effec...