NEUROPSYCHOLOGICAL DOSE EFFECTS OF A FREON, TRIFLUOROMETHANE (FC-23),COMPARED TO N2O

Animal studies show FC-23 to be a promising magnetic resonance imaging indicator of regional cerebral blood flow. In a Phase 1, dose ranging (investigative new drug) study, neuropsychological (NP) tests, subjec tive ratings, and intensive physiological monitoring were used to dete rmine the maximum tolerated concentration of FC-23 for human applicati on. Five normal healthy male volunteers were exposed to concentrations of FC-23 between 10% and 60% [randomly interleaved with exposures to both room air and 40% nitrous oxide (N2O)] in a within-subjects, doubl e-blind design. Analyses of individual cases and ranked group data sho wed that individuals tolerated the 30% concentration of FC-23 accordin g to established criteria. Planned comparisons indicated that inhalati on of FC-23 produced smaller NP changes and fewer negative symptoms th an 40% N2O but poorer NP performance and more negative symptoms than r oom air. This study indicated that FC-23 is not inert and that humans do not tolerate concentrations suitable for current MRI technology. NP and subjective data assisted in characterizing the sedative effect of FC-23. (C) 1998 Elsevier Science Inc.