A Randomized Trial of Oral and Transdermal Rivastigmine for Postural Instability in Parkinson Disease Dementia

Objectives The objective of this study was to compare the efficacy and safety of oral and transdermal rivastigmine for postural instability in patients with Parkinson disease dementia (PDD) who were candidates for a cholinesterase inhibitor. The primary outcome was the change in mean velocity of the center of pressure (CoP) after 6 months. Secondary outcomes included structural parameters of dynamic posturography, clinical rating scales, and adverse events requiring dose reduction. Methods Patients with PDD were randomized in a 1:1 ratio to oral or transdermal rivastigmine with target doses of 6 mg twice daily and 9.5 mg/10 cm(2) daily, respectively. Outcomes were assessed at baseline and 6 months. Results were compared within and between groups. Results Nineteen patients completed the study (n = 8 oral, n = 11 transdermal). Mean daily doses of 9.4 (1.5 mg) and 16.4 (+/- 3.6 mg) were achieved in the oral and transdermal groups, respectively. The transdermal group demonstrated a significant 15.8% decrease in mean velocity of CoP (patch: P < 0.05; oral: 10.0% decrease, P = 0.16) in the most difficult scenario (eyes closed with sway-referenced support). There was no difference between groups (P = 0.27). For structural parameters, significant improvements were seen in the mean duration of peaks (patch) and interpeak distance (oral) in the most difficult condition. No changes were observed in clinical rating scales. Six patients experienced nonserious adverse events requiring dose reduction (n = 5 oral; n = 1 transdermal). Conclusions Rivastigmine may improve certain elements of postural control, notably the mean velocity of CoP. Benefits appear to be more obvious under more taxing sensory conditions.