Effects of isoproterenol in panic disorder patients after antidepressant treatment

Fourteen panic disorder patients were infused with isoproterenol both before and after treatment with tricyclic antidepressants. Thirteen patients had panic attacks before treatment, and only 2 after treatment. There was a significant decrease in anxiety as measured by a Panic Description Scale during posttreatment infusions, and patients were able to tolerate longer infusions posttreatment. Isoproterenol increased systolic blood pressure and decreased diastolic blood pressure in both untreated patients and in 10 normal controls. Tricyclic antidepressant treatment of panic disorder patients abolished isoproterenol-induced increases in systolic blood pressure, but did not affect diastolic blood pressure response. These changes are consistent with a decrease in sensitivity to beta-1 receptor stimulation after treatment with tricyclic antidepressants.