Penetration Enhancement Strategies for Intradermal Delivery of Cromolyn Sodium

This study aimed to explore the use of chemical and physical enhancement strategies for the intradermal delivery of cromolyn sodium (CS) for treatment of atopic dermatitis. CS gels were formulated to individually contain 2.5 and 9% salcaprozate sodium (SNAC) as a potential chemical enhancer. The effect of microneedles, alone and in combination with SNAC, was investigated via in vitro permeation studies. Skin impedance and FTIR evaluation of SNAC-treated stratum corneum (SC) was done and compared to the control. The amount of drug delivered in the dermis after 24 h by the 2.5% and 9% SNAC gels was 23.29 ± 1.89 µg/cm² and 35.87 ± 2.23 µg/cm², respectively, which were significantly higher than the control (p < 0.05) but were not remarkably different from each other (p > 0.05). Microneedles enhanced permeation in both the control and 2.5% SNAC groups (p < 0.05); however, no synergistic enhancement was observed when microneedle and SNAC treatments were combined (p > 0.05). Over 24 h of treating the SC with 2.5% SNAC, FTIR evaluation showed stretches on the CH₂ asymmetric and symmetric stretching vibrations observed at 2920.23 cm^-1 and 2850.79 cm^-1 respectively in untreated SC, which shifted to higher wavenumbers and indicated some lipid fluidizing effect. However, no significant drop in skin impedance was seen with SNAC as compared to the control (p > 0.05). SNAC was concluded to have skin permeation enhancement effect on CS, while microneedles effectively enhanced CS permeation even in the absence of SNAC.