Bioavailability Study of a Transdermal Patch Formulation of Rivastigmine Compared with Exelon in Healthy Subjects

Rivastigmine is a reversible cholinesterase inhibitor indicated for the treatment of all stages of Alzheimer's disease (AD). Transdermal patch formulation allows smooth and continuous drug delivery. Its tolerability, efficacy and convenience of use increase treatment compliance. This study was designed to evaluate the bioavailability and to assess the bioequivalence of two rivastigmine transdermal patches at steady state (RIV-TDS Test Product versus Exelon Marketed Reference Product), with a release rate of 13.3 mg/24 h, after multiple patch applications. As secondary objectives, safety, patch adhesion and skin irritation were evaluated. This was an open-label, randomized, balanced, two-period, two-sequence, cross-over study of healthy adults (n = 31). The treatment period consisted of two 5-day study periods during which consecutive daily application of the investigational patches with a release rate of 13.3 mg/24 h rivastigmine took place. Serial blood samples were collected to measure plasma concentrations. Adhesion and skin irritation assessments were performed after application of patches. Point estimates and 90% confidence intervals of pharmacokinetic parameters at steady state, viz. area under the plasma concentration versus time curve from dosing time to the end of the dosing interval τ (profile day) at steady state [AUC0–τ,ss] (97.4; 88.8–106.9), maximum plasma concentration within the dosing interval τ (profile day) at steady state [Cmax,ss] (99.6; 90.4–109.7) and trough plasma concentration at the end of the dosing interval τ (profile day) at steady state [Cτ,ss] (96.8; 86.2–108.9), demonstrated that both patches were bioequivalent. Evaluation of patch adhesion showed better skin adherence for RIV-TDS as well as dermal response scores (skin tolerability after removal). For both products, bioequivalence was shown and systemic tolerability was in accordance with the safety profile of the drug substance. The trial is registered in ClinicalTrials.gov: NCT03573050 and EudraCT: 2018-000968-28.