Plasma 3-methoxy-4-hydroxyphenylethylene glycol (MHPG) and growth hormone responses to yohimbine in panic disorder patients and normal controls

Eleven patients with a DSM-III diagnosis of panic disorder and seven normal controls received yohimbine (20 mg) or placebo orally in a double-blind paradigm on two separate days. Compared to normal control subjects, the panic disorder patients had similar behavioral responses to placebo but a greater anxiogenic response to yohimbine. Compared to placebo, yohimbine produced a significant increase in plasma 3-methoxy-4-hydroxyphenylethylene glycol (MHPG) levels (p<0.02), with a trend toward greater MHPG rises in the panic disorder patients compared to the normal controls. In the patients, but not in the controls, there was a significant positive correlation between yohimbine-induced peak changes in MHPG and increased ratings of panic anxiety. Yohimbine had no effect on plasma growth hormone (GH) levels in either patients or controls. These results are discussed within the context of the noradrenergic theory of panic disorder.