Modeling of flux through silicone membranes from water

Do the Roberts–Sloan (RS) or modified Kasting–Smith–Cooper (KSC) equations that provide good fit to data for maximum flux, from water through mouse or human skin also provide a good fit to data for maximum fluxes through silicone membranes (polydimethylsiloxane, PDMS). The maximum fluxes through silicone membranes from water (JMPAQ), molecular weights (MW), solubilities in isopropyl myristate (SIPM) and water (SAQ) of 31 prodrugs and one parent drug have been fitted to the RS equation, which includes a parameter for dependence on SAQ, and the KSC equation, which does not, to determine which equation gave the better fit. In addition, the JMPAQ, MW, SAQ and solubilities in octanol (SOCT) of 26 diverse molecules from other laboratories were collected and fitted to the RS and KSC equations to determine if the choice of lipid parameter (SIPM or SOCT) had an effect on which equation gave the better fit. RS gave the better fit to the present prodrug database where: log JMPAQ = −2.454 + 0.716 log SIPM + 0.284 log SAQ + 0.00208 MW, r2 = 0.77. RS also gave the better fit to the database from other laboratories where: log JMPAQ = −2.046 + 0.667 log SOCT + 0.333 log SAQ − 0.00374 MW, r2 = 0.878 after four obvious outliers were removed to give n = 22. Thus, data for JMPAQ can be fitted to the RS equation, which also provides the best fit to maximum flux from water through mouse or human skin and includes a dependence on SAQ.