Panic attack frequency and vulnerability to anxiogenic challenge studies.

Intravenous lactate infusion and 60 mg oral fenfluramine challenges were administered to 26 patients with panic disorder (PD) and 12 age- and sex-matched control subjects. PD patients had significantly greater anxiety responses to either challenge than controls. When a panic attack frequency index scale of 1-4 was used, PD patients with more recent and more frequent spontaneous panic attacks scored higher on either challenge. There was a significant correlation between increasing panic attack frequency and greater anxiogenic responses to lactate and fenfluramine. Nine of 12 patients (75%) with high attack frequency (defined as having one or more panic attacks per week) reacted positively to both challenges in contrast to 0 of 14 PD patients with low frequency (less than or equal to 1 attack/month). The findings suggest that the current heightened anticipatory state of the patient (influenced by recent spontaneous panic attacks) rather than putative underlying trait factors predominates in the evocation of experimentally induced anxiety reactions. Future studies must consider the frequency of recent spontaneous panic attacks in the evaluation of anxiogenic reactivity to provocative stimuli.