Pharmacologic Effect of Toloxatone on Reactivity to the 35% Carbon Dioxide Challenge

The effect of a short treatment (7 days) with the reversible monoamine oxidase type A inhibitor toloxatone on the reactivity to the inhalation of 35% CO2 was evaluated in 18 panic patients who responded to 35% CO2 inhalation with panic before treatment. A single-blind, placebo-controlled design was applied. Panic patients were randomly assigned to the toloxatone (N = 10) or placebo (N = 8) groups and were given the 35% CO2 challenge on days 1 (before starting the treatment), 3, and 7. Patients on placebo did not report any significant changes in their reactivity to 35% CO2 during the three sessions, whereas patients on toloxatone reported a significant attenuation of the reactivity on day 7. These results indicate that (1) anxiety provoked by the inhalation of 35% CO2 is reproducible; (2) placebo has a negligible effect on 35% CO2 reactivity; and (3) reactivity to 35% CO2 is significantly attenuated by short treatment with toloxatone, possibly related to its antipanic activity.