Innovative Long-Acting Bisoprolol Patch: Synergistic Ion-Pair Skin Adsorption for Drug Delivery Control Coupled with Dynamic Modulation of Penetration Enhancers

This study aims to develop a sustained release patch for bisoprolol (BSP) to address the issue of blood pressure fluctuations caused by traditional dosing methods, ensuring continuous drug release and efficient utilization. Long-chain saturated fatty acids (C6–C12) were chosen as counterions to precisely control BSP's permeation rate in the patch formulation, and the ion-pairing strategy's mechanism in drug delivery was thoroughly investigated. Molecular docking results revealed significant differences in the adsorption capacities of different ion pairs in the stratum corneum (SC) and epidermis, directly influencing their residence times and thereby regulating BSP's passive diffusion rate. Particularly, the BSP-C10 ion pair successfully reduced BSP's permeation rate to one-third of its baseline. To enhance drug delivery efficiency and reduce costs, chemical permeation enhancers (CPEs) are typically added to sustained release patches. In contrast to traditional static analyses based on cumulative permeation, this study utilized ATR-FTIR dynamic detection of isopropyl myristate (IPM) as a preferred enhancer, studying its disruptive effects on the skin barrier during drug delivery. The study observed that during drug delivery, the interaction between IPM and skin lipids follows a U-shaped trend: initially increasing, then decreasing, with the peak occurring at 10 h. Similarly, the drug delivery rate displays a comparable pattern. The addition of IPM as CPE increased the patch utilization rate from 39.8 ± 4.31 to 79.8 ± 7.27%. This strategy aims to rapidly reduce blood pressure in the initial phase with subsequent weakening of IPM disruption, allowing the ion-pairing strategy to dominate drug delivery control and maintain stable long-term therapeutic effects. Pharmacokinetic studies demonstrated that the newly developed BSP sustained release patch maintains stable blood drug concentrations, reduces burst release effects, increases bioavailability to 84.679%, doubles MRT0–t, halves Cmax, and significantly reduces the occurrence of blood pressure fluctuations.