[A phase 3 clinical trial of 123I-iomazenil, a new central-type benzodiazepine receptor imaging agent (Part 1)--report on clinical usefulness in diagnosis of various brain diseases].

Iomazenil (IMZ) is a partial inverse agonist of central-type benzodiazepine receptors (BZR) which binds specifically to BZR with high affinity. The safety and clinical effectiveness of 123I-IMZ SPECT in the diagnosis of brain diseases were evaluated in 655 patients with various brain diseases, such as epilepsy, cerebrovascular diseases, degenerative diseases and mental disorders relating to BZR. This was a Phase 3 study conducted as a multicenter trial at 52 collaborating institutions. There was no significant adverse reactions in the clinical symptoms or abnormal laboratory test values. The investigators judged 123I-IMZ SPECT to be effective in 95% of 638 analyzed cases. The injected dose did not correlate with the image quality or the clinical effectiveness of 123I-IMZ SPECT, suggesting that these items depend largely on the characteristics of the apparatus used, the disease or pathology of the patients, rather than the dose. We conclude that 123I-IMZ imaging is safe and provides effective information based on BZR binding which is useful in the diagnosis of various brain diseases.