Development of Medicated Chewing Gum Formulations for the Delivery of a Poorly Soluble Drug

The concept of chewing gum for medical purposes provides discrete, convenient administration, the potential for buccal absorption and the avoidance of first pass metabolism or gastrointestinal degradation. This work contributes to the limited information available on the release of poorly soluble drugs from medicated chewing gum formulations. Lansoprazole was chosen as a model drug due to its poor solubility and instability (under acidic conditions), thus a chewing gum formulation would be of particular benefit avoiding gastrointestinal degradation.
The solubility and stability of lansoprazole in artificial saliva was found to be dependent on the pH of the solution. An increase in pH caused an increase in solubility with a significant increase between pH 9 and pH 10. At pH 6, concentrations decreased over time confirming the acid instability of lansoprazole. The use of cyclodextrins as solubilisers and stabilisers for lansoprazole were investigated; complexed lansoprazole (with Mβ-CD, 1:1) resulted in a 9 fold increase in solubility compared to free lansoprazole and remained stable at pH 6.
Chewing gum formulations incorporating lansoprazole were prepared and the following excipients were investigated: Revolymer‟s® hydrophilic polymer Rev7, buffering excipients and complexed lansoprazole (with Mβ-CD, 1:1). Drug diffusion from gum surfaces was found to be limited, highlighting the need for effective mastication to ensure the timely release of the drug. In vitro release was evaluated using the EP approved masticator. Various parameters were investigated including: the type of dissolution medium, pH, chew rate and sampling and replacement volumes. Significant differences in release after 30 minutes mastication were found for gums containing Rev7 and potassium carbonate (both of which contributed to increasing the hydrophilic capacity of the gum). These gums were also softer than other formulations due to a plasticising effect on the gum base elastomer resulting in softer, less cohesive gums. Complexation was not found to have an impact on in vitro drug release from gums.
The study also assessed the buccal absorption of free lansoprazole and complexed lansoprazole (with Mβ-CD, 1:1) using porcine buccal mucosae. The highest partitioning coefficient was observed for free lansoprazole at pH 6.8 due to a lower ionised fraction in combination with a lower molecular weight. Complexed lansoprazole had the highest drug flux but also had the paradoxical effect of decreasing the permeability coefficient.
Overall the study contributed to increasing the understanding of factors governing the release of a poorly soluble and unstable API, lansoprazole, from a medicated chewing gum formulation. The optimised formulation would contain lansoprazole, 8 % Rev7 and potassium carbonate to provide the maximum release of drug from the gum and also facilitate buccal absorption.