Fenfluramine provocation of anxiety in patients with panic disorder.

Fenfluramine, and indirect serotonergic agonist, was administered to nine women with panic disorder, nine women with major depressive disorder, and nine women controls. Panic disorder patients revealed significantly greater anxiogenic responses to fenfluramine administration at all 5 hourly measurement points than either depressed patients or control subjects. Prolactin and cortisol responses to fenfluramine were also significantly greater in panic disorder patients than in either depressed patients or control subjects. Placebo administration did not elicit robust or significantly different anxiety or hormonal responses in panic disorder patients or control subjects. These data offer evidence that serotonergic hyperresponsivity must be considered as an important factor in the mechanism of events provoking overt panic attacks.