Modulation of hyperreactivity to 35% CO2 after one week of treatment with paroxetine and reboxetine: a double-blind, randomized study.

The effects of short treatments (7 days) with paroxetine and with reboxetine on the reactivity to inhalations of 35% carbon dioxide (CO 2 )/65% oxygen (O 2 ) were compared in 28 patients with Panic Disorder who had positive responses to 35% CO 2 inhalations. A double-blind, randomized design was applied. Each patient was given the 35% CO 2 challenge on days 0 (before starting the treatment) and 7. Anxiety reactivity to CO 2 decreased significantly with both drugs but the decrease was significantly stronger in the group treated with paroxetine. The rate of patients whose reactivity has reduced of at least 50% after 7 days was significantly higher in the group treated with paroxetine (10/14, 71.5%) than in the one treated with reboxetine (3/14, 21.5%). These results indicate that the modulation of the serotonergic system is more relevant for CO 2 hyperreactivity than the modulation of the noradrenergic one.