Noradrenergic function in panic disorder. Effects of intravenous clonidine pretreatment on lactate induced panic

To assess the role of noradrenergic stimulation during lactate-induced panic, ten patients with panic disorder who panicked during a standard sodium-lactate infusion underwent a repeat infusion following intravenous clonidine pretreatment. Although clonidine significantly lowered prelactate systolic blood pressure, the drug did not significantly lower prelactate anxiety levels, as reflected by the Acute Panic Inventory (API). Clonidine blocked lactate-induced panic in four of ten subjects, a significant effect. Clonidine treatment also significantly attenuated lactate-panic symptoms, as reflected by time to panic and API comparison between trials. Nevertheless, over half the subjects still panicked in response to lactate despite clonidine. This preliminary study suggests that reduction of central noradrenergic activity by clonidine, at least at the dosage levels employed in the current study, only partially attenuates panic response to lactate. Noradrenergic theories of panic may not therefore fully account for lactate panicogenesis.