The influence of the ageing process on the low-frequency behaviour of some electrical parameters of 5 percent dipirone syrup and 5 percent sodium picosulphate solution is studied. The impedance measurements were performed in the range between 0.05 kHz and 1 MHz, using the HP 16452 cell for liquids connected to the HP 4284A impedance analyzer. The electrode separation was changed with spacers of different thickness provided by the manufacturer in order to correct the effect of the electrode polarization on the experimental results. The drug ageing state was artificially generated by dilution or heating processes. The results show that the dielectric technique can be used as a good quality complementary control for evaluation of the ageing.