Targeting tacrolimus to deeper layers of skin with improved safety for treatment of atopic dermatitis

Atopic dermatitis (AD) is chronically relapsing eczematous skin disorder having significant impact worldwide. Tacrolimus is the drug-of-choice which inhibits T-cell activation resulting in suppression of inflammation. However, despite being effective, most common adverse events of tacrolimus are low-and-variable bioavailability, burning sensation and pruritus at application site, which prompt for development of novel carrier that could effectively target tacrolimus to site-of-action without producing undesirable side-effects. Tacrolimus-loaded lipid-nanoparticles (T-LN) were prepared and optimized. DSC and FT-IR have been employed to study drug-excipient incompatibility and encapsulation of drug in lipid which was further confirmed by 1H NMR. In vitro studies revealed much higher drug release, skin penetration and enhanced skin accumulation as compared to reference Protopic®. In vitro and in vivo occlusion studies demonstrated similar occlusiveness for T-LN and reference however; T-LN showed significantly higher drug levels penetrating into deeper skin layers where dendritic cells responsible for immunopathogenesis of AD mainly reside. In-vivo skin retention demonstrated 3.36, 30.81 and 28.68-times higher stratum corneum, epidermal and dermal levels respectively compared to reference. Visualization of cutaneous uptake in-vivo using CLSM confirmed targeting to deeper skin layers and Draize test showed no skin irritation with PII 0.00. Thus T-LN displayed superior performance, effective skin targeting and improved safety as compared to reference.