The dermal permeability coefficient (log K_p) of 14 drugs (temazepam, alprazolam, bromazepam, elenium, oxazepam, lorazepam, lormetazepam, clotrazepate, ranitidine, methyldopa, piroxicam, amizepine, paracetamol, aspirin) was estimated in silico using DERMWIN v. 2.0 software. RP-18 thin layer chromatographic retention data were collected using methanol-water mobile phases containing between 50 and 90% (v/v) of methanol. The retention factor (R_f) values were converted to R_M values following the equation: R_M = log (1/R_f -1).

R_M values were plotted against the concentration of methanol in the mobile phase (c_MeOH) and extrapolated to zero concentration of methanol following the linear equation: R_M = R_M⁰ + S c_MeOH.

R_M⁰ and S chromatographic parameters were found to be connected with log K_p via reversed parabolic relationships explaining over 93% of total variability.

This research was supported by an internal grant of the Medical University of Łódź no. 503/3-016-03/503-31-001