The relationship of panic disorder and its treatment outcome to 24-hour urinary MHPG levels.

Levels of 24-hour urinary 3-methoxy-4-hydroxyphenylglycol (MHPG) were not markedly elevated in a group of 35 panic disorder patients when compared to healthy controls (mean = 2,430 micrograms/day vs. 2,130 micrograms/day). There was a weak association between elevated pretreatment levels of MHPG and a positive treatment response to alprazolam or diazepam. Alprazolam and diazepam may differ in their effects on MHPG.