Predictors of the Pressor Response to the Norepinephrine Transporter Inhibitor, Atomoxetine, in Neurogenic Orthostatic Hypotension

Abstract

We previously reported that the norepinephrine transporter inhibitor, atomoxetine, improved standing blood pressure and lightheadedness in patients with neurogenic orthostatic hypotension (nOH). The purpose of the present study was to determine the predictors of the pressor response to atomoxetine. Patients with nOH who participated in the clinical trials ( https://www.clinicaltrials.gov ; Unique identifiers: NCT00223691 and NCT01316666) were included in this retrospective analysis. All subjects underwent autonomic function testing, plasma norepinephrine, systolic, diastolic blood pressure, and symptoms assessments, whereas seated and standing, before, and 60 minutes after a single dose of atomoxetine 18 mg. A subset of 25 patients underwent iodine-123–labeled metaiodobenzylguanidine scanning to estimate the degree of cardiac sympathetic denervation. A total of 99 subjects with nOH (67±9 years old, 40 women) participated in the study, 35 with multiple system atrophy, 52 with pure autonomic failure, and 12 with Parkinson disease. The average orthostatic decrease in their systolic blood pressure/diastolic blood pressure was −52±26/−22±15 mm Hg. Supine plasma norepinephrine levels predicted the standing systolic blood pressure (adjusted R 2 was 0.12, F [3,80]=4.66, P =0.007) and diastolic blood pressure (adjusted R 2 was 0.18, F [3, 80]=7.04, P =0.001) in response to atomoxetine. The increase in systolic blood pressure after atomoxetine was associated with the decrease in nOH-related symptoms ( R 2 =0.14, F [1,44]=8.16 P =0.007). In conclusion, plasma norepinephrine was modestly associated with the pressor response to atomoxetine in patients with nOH. Additionally, the improvement in nOH-related symptoms was associated with the increase in the pressor response to atomoxetine.