Purpose To determine the formulation composition of a transdermal drug delivery system of indomethacin,MASCOS 10 pressure sensitive adhesive was used to prepare a drug-in-adhesive type patch containing a variety of permeation enhancers (i.e.azone, l-menthol, isopropyl myristate (IPM), tween-80 and oleic acid).Methods Differential scanning calorimetry was used to evaluate the compatibility between indomethacin and MASCOS 10.The enhancing effects of the permeation enhancers were evaluated using two-chamber side-by-side diffusion cells containing excised rat skin.Results The results obtained indicate that 5% azone and 5%l-menthol were selected for the optima formula.Conclusion In conclusion, the present data confirm the feasibility of developing indomethacin transdermal patches on an industrial scale.Further studies, now in progress, will deal with the application of the presently reported findings to human skin permeation, involving in vivo testing.