The purpose of the present study was to evaluate the effect of ion pairing on the skin permeation of amlodipine. Amlodipine base (AM) was first prepared from amlodipine besilate (AM-B), then amlodipine adipate (AM-A), amlodipine oxalate (AM-O) and amlodipine maleate (AM-M) were prepared using AM and the corresponding organic acids. Differential scanning calorimetry (DSC) thermogram studies demonstrated the formation of complexes between AM and the various acids. In vitro percutaneous absorption of AM and its complexes was evaluated through excised rat skin using 2-chamber diffusion cells. The results showed that AM had the greatest steady-state flux and lowest permeability coefficient of the five compounds from the El system (ethanol:isopropyl myristate (IPM)= 2:8), and its four complexes all exhibited a lower flux and higher permeability coefficient than AM.