Evaluation of a multicentre study with Iomazenil--a benzodiazepine receptor ligand.

After showing in an earlier publication that Iomazenil is a potent benzodiazepine receptor antagonist, the substance has been distributed to 11 clinical centres in Europe for further tests. The protocol asked for volunteers, epileptic cases and patients with Alzheimer's disease. Prior to the Iomazenil examination, flow images by perfusamine or HMPAO were required, and as comparative methods EEG, computed tomography (CT) and magnetic resonance imaging (MRI) were performed. The results allowed first the determination of the normal distribution of the benzodiazepine receptors in the human brain. The highest uptake was found in medial occipital cortex. Second, the evaluation of the epileptic cases shows a 100% positive prediction value for Iomazenil compared to 92% for flow images. Negative prediction values were calculated as 81% for Iomazenil and 54% for flow images. Furthermore, one group reported the successful diagnosis of Alzheimer's disease at an early stage. The visual image examination was tentatively compared to a more objective semiquantitative one based on quotients of corresponding left/right regions of interest. This semiquantitative method has not proved successful yet, but the problems have been identified. A more precise protocol for further studies is therefore proposed.