Evaluation of adhesive properties of transdermal therapeutic systems containing nitroglycerin

The patch performances and the success of the transdermal drug delivery can be significantly affected by the quality of contact between the patch and the skin. Poor adhesion will dramatically reduce percutaneous delivery. In this study the adhesive properties (peel force and creep resistance) of three monolayer self-adhesive nitroglycerin (NTG) patches available on the market, Deponit, Minitran, and Triniplas, were compared. The patches were characterized also in terms of in vitro drug release and ex vivo skin permeation. The creep resistance values verified in the case of Deponit and Triniplas indicated a low cohesion of these matrices. The peel force values were in the accepted range, even if Triniplas and Deponit showed values double that shown by Minitran. The percentage of NTG released in vitro after two hours in all cases exceeded ninety percent. The ex vivo permeation profiles were similar, even if the three patches had different loaded amounts and surface areas. The measured permeated amount, 11 mg permeated in 24 h, was predictive of the claimed in vivo release (10 mg in 24 h).