Lactate vulnerability after alprazolam versus placebo treatment of panic disorder

Thirty-six patients with panic disorder underwent sodium lactate infusion before and after 8 weeks of treatment with alprazolam or placebo. With reinfusion, those patients panic-free with chronic alprazolam treatment displayed significantly decreased reactivity to lactate, as measured by subjective symptom ratings, duration of infusion before developing peak lactate-induced symptoms, and the proportion of patients experiencing lactate-induced anxiety or panic. Patients panic-free on placebo, as well as nonresponders to alprazolam treatment, displayed some, although less striking, decreases in reactivity to lactate with reinfusion. As a group, patients clinically unchanged with placebo treatment showed no systematic change in lactate response with reinfusion. Although the small numbers of patients in each treatment outcome group prohibit drawing definitive conclusions, these findings suggest that decreases in lactate-induced panic after successful alprazolam treatment of panic may result from a combination of changes in clinical state and direct effects of the medication.