A review of patient-specific gastrointestinal parameters as a platform for developing in vitro models for predicting the in vivo performance of oral dosage forms in patients with Parkinson's disease.

Parkinson's disease (PD) is a progressive neurodegenerative disease that presents with visible motor symptoms, but that is accompanied by several additional symptoms, including gastrointestinal symptoms that may affect pharmacokinetics of oral medications. A detailed understanding of the nature of PD-specific gastrointestinal parameters and of how they may affect drug release of orally administered dosage forms seems to be essential information for developing better oral PD medications. The availability of bio-predictive drug release models simulating PD-specific gastrointestinal parameters would also be beneficial for this purpose. The focus of the present literature review was to determine PD-specific gastrointestinal parameters that will allow for the development of a test methodology simulating the gastrointestinal passage of orally administered medications in PD patients. Whereas for some gastrointestinal segments there is quite a reasonable set of data available on fluid volumes, motility and passage times, for others there is still a big lack in information that would be required for simulating a detailed gastrointestinal passage in a PD patient. The latter is particularly true for potential disease-related changes in gastrointestinal fluid composition. However, with the availability of novel non-invasive diagnostic options there is a chance of obtaining more information in the near future.