Topical treatment of rosacea: update and outlook.

Rosacea is an inflammatory skin condition that typically requires long term management. It is characterized by redness of the face, dilation of facial capillaries, the appearance of pimples and pustules, and it may lead to advanced conditions such as skin lymphoedema and rhinophyma. Initially, treatment involved oral drug administration, but a number of topical formulations have been developed as medicines to manage this skin disorder. Many rosacea patients have sensitive skin and side effects from current topical therapies have been shown to impact seriously on patient adherence to topical therapy regimens and clinical success. Notwithstanding this, no new topical products for management of rosacea have been made available since 2015. This review considers alternative formulation strategies that have been investigated for the most commonly prescribed topical drugs for rosacea, namely, metronidazole, azelaic acid and ivermectin. The pharmacokinetics and metabolism of each molecule are also discussed as this information is an essential starting point for required local tissue target concentrations. Attention is focused on evaluation of formulations with either in vitro permeation testing or in vivo studies. Finally, the limitations of studies published to date are highlighted as well as the likely barriers hindering translation of novel therapies from the laboratory to the market.