In vitro permeation studies were done using modified Franz diffusion cell through rabbit skin and silicone membrane utilizing different ratios of oleic acid with diclofenac diethylamine (DDA) in normal saline and methanol mixture during present study. Solubility studies indicated linear increase in drug solubility with carrier concentration. The enhancing effect of all the enhancer’s ratios was found to be significantly greater than that of standard without enhancer (control). ‘Benchmark’ values with which to compare the performance of the vehicle are the flux values which were statistically no significant difference (P>0.05) across rabbit skin and silicone membrane. The input-rate values of all the ratios have shown a constant trend. The vehicles used were predominantly influencing the partition of the drug into the skin rather than the diffusion throughout the study. Consequently, changes in diffusion and/or partition may occur as a result of absorption or depletion of permeation enhancer inside the membrane/or skin over time which validates our results.