The fluctuation index (FI), a measure of the relative difference between peak and trough concentrations((Cmax-Cmin)/ Cavg), was 0.58 for Exelon 4.6 mg/ 24 h transdermal patches and 0.77 for Exelon 9.5 mg/ 24 h transdermal patches, thus demonstrating a much smaller fluctuation between trough and peak concentrations than for the oral formulation (FI = 3.96 (6 mg/ day) and 4.15 (12 mg/ day)).