In another series of studies, Liu et al. investigated the effect of chemical enhancers, ultrasound, and electroporation treatment, either individually or in-series, on the transdermal uptake and delivery of the uncharged immunosuppressant Cyclosporine A (molecular weight of ~1200 g/mol) (Liu et al. 2006, 2010). Note that the treatment modality in this case is significantly different than in the study conducted by Kost et al. (Kost et al. 1996), because the electroporation, ultrasound, and chemical enhancer treatments were all decoupled and occurred in series, rather than with simultaneous application. In both publications by Liu et al., if applied, chemical enhancers (azone, sodium cholate, sodium thiosulfate, menthol, N-Methyl pyrrolidine, dimethyl sulfoxide, and sodium dodecyl sulfate at varying concentrations in ethanol or water), were utilized first to treat skin samples for an incubation time of 2 h. The chemical enhancer solution was then replaced with a 0.5 % Cyclosporine A in 60 % saline/40 % ethanol solution to be used as the coupling medium for both electroporation and ultrasound treatment. Then, if applied, the skin was treated with 110 V electric pulses every 20 s (300 ms pulse length) for 10–20 min. Finally, if applied, ultrasound treatment was conducted, at a frequency of 20 kHz, an intensity of 0.8 W/cm², a 50 % pulse length (1 s ON: 1 s OFF), a transducer to skin distance of 0.5 cm, and a total treatment time of 30 min (Liu et al. 2006, 2010). Based on the mode of treatment of each enhancer in these studies, which effectively decoupled their ability to interact with one another, one would not expect to observe a large extent of synergism, which was the case. Only modest enhancements over controls were reported when ultrasound and electroporation were combined, with slightly higher delivery when a trimodal treatment, including an azone pretreatment, was utilized. These mild “synergistic” interactions were attributed to partial disorganization of the stratum corneum lipids, making them more susceptible to the other modes of treatment (Liu et al. 2006, 2010). Subsequent histological examination of the skin under these different treatment regimens showed no evidence of structural damage. Subsequent studies have further investigated the use of in-series treatment utilizing electroporation (1 ms, 300 V pulses) followed by 20 kHz ultrasound at 6.1 W/cm² for 2 min for the delivery of 4.4 kDa dextran labeled with fluorescein isothiocyanate (Petchsangsai et al. 2014). A synergistic increase in the measured flux was achieved compared to the flux achieved with either method alone (Petchsangsai et al. 2014). Other studies have noted only minimal enhancement as a result of the combination of electroporation with ultrasound utilizing an in-series treatment regimen, suggesting that the method is highly regimen dependent (Zorec et al. 2015).