Microneedle and iontophoresis mediated delivery of methotrexate into and across healthy and psoriatic skin

Psoriasis is a condition of the skin which involves scales, dry patches, and inflammation. Methotrexate (logP: -1.8, MW:454.44 g/mol) is administered orally or intravenously to treat psoriasis. The first-pass metabolism and systemic toxicity can be avoided by administration via skin. Topical and transdermal delivery of methotrexate using iontophoresis and microneedles, alone and in combination was investigated using full-thickness healthy human skin. It is also equally relevant to evaluate the delivery into and across damaged/diseased skin. Hence, this study investigated the delivery of methotrexate using ex vivo healthy and psoriatic human skin to understand the effect of skin disease condition on delivery of methotrexate via skin. A lower resistance and a higher TEWL for psoriatic skin indicated damaged barrier function, while histology studies indicated epithelial hyperproliferation and elongated rete ridges. Using the optimized iontophoretic parameters, there was no significant difference in receptor delivery for psoriatic skin (39.51 ± 4.45 µg/sq.cm) as compared to healthy skin (43.15 ± 0.83 µg/sq.cm). However, methotrexate delivery into psoriatic skin (126.23 ± 24.65 µg/sq.cm) was significantly higher as compared to healthy skin (12.02 ± 4.89 µg/sq.cm). Thus, significantly higher total delivery was observed from psoriatic skin than healthy skin.