Lack of effect of the combination of metyrapone and oxazepam on brain dopamine.

The combination of metyrapone and oxazepam (Met-Ox) has recently shown promise as a pharmacotherapy for cocaine use disorder. Metyrapone is available clinically and is typically used to diagnose adrenal insufficiency, while oxazepam is often prescribed to treat anxiety. The combination of low doses of metyrapone and oxazepam has been shown to significantly attenuate cocaine self-administration and cue-reactivity in rats, as well as decrease the number of subjects that used cocaine in a pilot clinical trial. Previous studies in rats suggest that the combination of these two drugs may decrease drug-related behaviors by reducing corticosterone synthesis in the medial prefrontal cortex. Since corticosterone has been associated with increased brain dopamine, these reductions in central corticosterone produced by Met-Ox might be accompanied by a concomitant decrease in dopamine to thereby attenuate drug taking and seeking. Thus, these studies were designed to determine the effects of Met-Ox on dopamine in rats. In vivo microdialysis studies in the medial prefrontal cortex and nucleus accumbens revealed that Met-Ox produced no measurable effects on cocaine-induced increases in dopamine. Further, the combination of these two drugs produced no effect on dopamine in the absence of cocaine. Together, these studies demonstrate that Met-Ox does not exert its effects by altering dopamine, suggesting that it might be possible to treat cocaine use disorder without affecting dopamine, which would lead to reduced side effects and increased compliance.