Summary
Introduction – Pulmonary delivery of levodopa offers a rapid treatment for off episodes in Parkinson’s Disease. Inbrija is currently the only approved orally inhaled levodopa product, but a generic product (Levodopa Cyclops) is in development. These two products differ in terms of inhaler design and powder formulation (e.g. composition, particle size, and density), leading to differences in in vitro characteristics. The objective of this study is to assess whether differences in the in vitro characteristics between Levodopa Cyclops and Inbrija result in differences in their pharmacokinetic profiles. Methods – The in vitro dissolution characteristics were assessed using a Paddle Apparatus, and the in vitro aerosol characteristics were evaluated using an NGI. A clinical trial in fasted, healthy volunteers was performed to investigate the pharmacokinetics of both levodopa inhalation products. Results and Discussion – This study showed that the in vitro dissolution rate of Levodopa Cyclops was substantially higher than the in vitro dissolution rate of Inbrija. Since dissolution is a prerequisite for absorption, it was expected that the in vivo absorption of Levodopa Cyclops would be faster. However, the pharmacokinetic profiles of both products, including the absorption phases, were similar. This may indicate that the rate of levodopa absorption from the lungs is not limited by the dissolution of the dry powder formulation.