MIAMI—Droxidopa is associated with reductions in fall risk and dizziness or lightheadedness among users and nonusers of dopamine decarboxylase inhibitors (DDCIs), according to research described at the Second Pan American Parkinson’s Disease and Movement Disorders Congress. These findings from an open-label, observational study “support previous data showing the efficacy of droxidopa for neurogenic orthostatic hypotension symptom reduction, even with concomitant DDCI use,” said the researchers.

Neurogenic orthostatic hypotension—a sustained blood pressure drop upon standing due to deficient norepinephrine release—is common among patients with disorders associated with autonomic nervous system dysfunction (eg, Parkinson’s disease, multiple system atrophy, and pure autonomic failure). Symptoms include lightheadedness or dizziness, presyncope, syncope, and falls.

Steven Kymes, PhD

Droxidopa, a prodrug of norepinephrine, is approved to treat symptomatic neurogenic orthostatic hypotension. Droxidopa is converted to norepinephrine by dopamine decarboxylase, which also converts levodopa to dopamine. Patients with Parkinson’s disease are commonly treated with DDCIs in conjunction with levodopa treatment. DDCIs did not appear to interfere with the therapeutic efficacy of droxidopa in clinical studies, but “high doses of DDCIs (8- to 10-fold higher than clinical doses) have been shown to blunt the effects of droxidopa,” said Steven Kymes, PhD, Director of Health Economics and Outcomes Research at Lundbeck in Deerfield, Illinois, and colleagues.

A Post Hoc Analysis

To assess the long-term efficacy of droxidopa for the treatment of neurogenic orthostatic hypotension in patients concomitantly receiving DDCIs, Dr. Kymes and colleagues conducted a post hoc analysis of outcomes related to falls and neurogenic orthostatic hypotension symptoms in patients using DDCIs versus patients not using them. The researchers used data from a six-month open-label, prospective, observational study of patients newly initiating droxidopa.

Eligible participants were 18 and older; had underlying Parkinson’s disease, multiple system atrophy, pure autonomic failure, dopamine beta-hydroxylase deficiency, or nondiabetic autonomic neuropathy; were newly initiating droxidopa; and were able to speak and understand English. The researchers excluded patients with a self-reported diagnosis of dementia, Alzheimer disease, schizophrenia, or other psychiatric disorder, as well as those who were nonambulatory or confined to a wheelchair.

Researchers used a patient falls questionnaire to record the number of falls in the past month at baseline and at one, three, and six months. They also used the Orthostatic Hypotension Symptom Assessment (OHSA) Item I test to assess dizziness or lightheadedness. All outcomes were self-reported.

Investigators then compared baseline differences using chi-square tests for categorical variables and t-tests for continuous variables. “The influence of DDCIs on risk of falling and OHSA Item I scores was compared across time points using generalized linear mixed models (logistic for risk of falling) adjusting for repeated measures within individuals,” said the researchers.

Droxidopa Treatment Was Associated With Reduced Falls

A total of 168 patients were included in this study; 55 were DDCI users, and 113 were non-DDCI users. The mean age in the DDCI group was 75, and the mean age in the non-DDCI group was 57. There were 19 women (34.5%) in the DDCI user group and 68 (60.2%) in non-DDCI user group. Most participants were white in both groups (92.7% in the DDCI group and 81.4% in the non-DDCI group).

“There were significant differences in the primary diagnoses between the groups. Parkinson’s disease was the most frequent diagnosis in the DDCI group (89.1%), and autonomic failure with no cause identified was the most frequent diagnosis in the non-DDCI group (92.9%),” Dr. Kymes and colleagues said. “At baseline, 61.8% of patients receiving DDCIs and 46.9 % of patients not receiving DDCI reported at least one fall in the last month.” The mean OHSA Item I scores at baseline were 5 in the DDCI group and 6 in the non-DDCI group.

The proportion of patients receiving DDCIs who experienced one or more falls in the past month after six months of droxidopa treatment significantly decreased from baseline, with a 36.5% reduction over the course of the study.

Among patients not receiving a DDCI, there was a 6.2% reduction in falls over the course of the study, but the reduction was not significant. Changes in the proportion of patients reporting one or more falls in the past month from baseline to six months did not differ significantly between the groups.

In addition, patients receiving DDCIs and nonusers showed significant improvement in OHSA Item I scores from baseline after six months of droxidopa treatment (change of 1.5 and 1.9 units, respectively). The difference between groups was not statistically significant.

“Specifically designed studies are needed to further examine the impact of DDCIs on droxidopa because the current study sample was not powered for subgroup analyses and all data were self-reported by patients,” the researchers concluded.

—Erica Tricarico