Optimization of SIS-based hot-melt pressure-sensitive adhesives for transdermal delivery of hydrophilic drugs

Abstract To optimize hot-melt pressure-sensitive adhesives (HMPSAs) for transdermal delivery of hydrophilic drugs, styrene–isoprene–styrene copolymer (SIS), epoxidized SIS (ESIS), tackifiers, and plasticizer were melt-mixed with polyethylene glycol 2000 (PEG2000) or poly (ethyl acrylate-co-methyl methacrylate-co-trimethylammonioethyl methacrylate chloride) (RLPO). Their compatibility was studied with DSC and FT-IR. Their 180° peel strength and holding power was measured for their adhesive performances. In vitro drug release experiments were carried out using a modified Franz type horizontal diffusion cell, in which geniposide was chosen as a hydrophilic model drug. Although PEG2000 can greatly enhance the accumulative release rate of geniposide in a manner of burst release, its poor compatibility with the components of SIS/ESIS-based HMPSAs makes the adhesive performance hardly meet the practical requirement of transdermal drug delivery. RLPO not only provides sustained release behavior to geniposide through its low content of quaternary ammonium groups but also preserves excellent adhesive performance due to its partial compatibility with the components of SIS/ESIS-based HMPSAs. Therefore, RLPO is preferred to develop ideal SIS/ESIS-based HMPSAs for transdermal delivery of hydrophilic drugs.