Methods and apparatus for determining when a tablet has been removed from a blister pack are presented. A method includes measuring an electrical characteristic, such as electrical resistance or impedance, between at least two terminals that are in electrical communication with a lidding film included in the blister pack, wherein the removal of a tablet from the blister pack results in an opening in the lidding film, thereby giving rise to a finite change in the electrical characteristic. Another method determines the state of the blister pack using electrical resistance tomography or electrical impedance tomography.