A car driver was stopped twice by the police within a few days and tested for ethyl alcohol content in breath and blood. These tests revealed the presence of ethyl alcohol in significant concentrations in both breath and blood of the driver. The driver denied that he had drunk alcohol and explained the above mentioned test results by the fact that he had taken Isoket^® (isosorbide dinitrate – an oral aerosol preparation containing ethanol used in ischaemic heart disease) directly before the police testing. Experiments were performed, which showed that after administration of Isoket® aerosol, ethyl alcohol is not detected in blood; however, it significantly influences the amount of alcohol in exhaled air.