µL. The peak areas of the compounds (Acmp) and internal standards (AIS) were detected in extracted ion chromatograms from the mass spectrometer data in positive mode. The Acmp/AIS was calculated and logarithmized. From a plot of ln Acmp/AIS against the incubation time, the gradient (k value) was established. The t½ value and CLint were calculated according to the Cyprotex protocol [117] and compared with known fast and slow metabolically degraded standards of verapamil and diazepam (Table ). The identification of 7-OH-THA metabolite was confirmed by the retention time and HRMS spectrum of 7-OH-THA chemical standard. The amount of 7-OH-THA formed was expressed as peak area and related in % to 7-OH-THA peak area gained from THA HLM incubation.