Biol. Pharm. Bull. 29(8) 1717—1722 (2006)

potent, long-lasting b2-adreoceptor agonist effects. Clinical studies have revealed that it induces bronchodilation for at least 12 h after a single oral administration. However, in order to maintain effective plasma concentrations and suppress asthmatic fits, there is considerable interest in development of transdermal drug delivery systems. Transdermal drug delivery is well recognized as an alternative to oral delivery and has many advantages, including the avoidance of metabolism in the gastrointestinal tract and the liver, long-term maintenance of therapeutic plasma levels of drugs and ready discontinuation of drug input if side effects arise. However, without the use of skin permeation enhancers, systemic delivery of most drugs through the skin is limited due to the barrier function of the stratum corneum. Such agents increase drug transport through the skin by elevating partition and diffusion coefficients. Ideally enhancers should increase drug transport by reversibly altering the skin barrier function without sensitization or irritation. We have already reported effects of l-menthol and N-methyl-2-pyrrolidone (NMP) on skin permeability and stability of formoterol fumarate (FF) in matrix patches. Furthermore, efficacy under simulated conditions relevant to asthma in experimental animals was demonstrated. However, no significant effects were observed with 2-octyldodecanol (OD) on rat skin permeability of FF in solution. In the present study, we evaluated the skin permeability of FF and irritation of EVA matrix patches containing ethylcellulose (EC) and OD using different species of experimental animal.