Polymeric systems for amorphous Δ9-tetrahydrocannabinol produced by a hot-melt method. Part I: Chemical and thermal stability during processing

The objective of the present research was to investigate the stability of an amorphous drug, Δ9-tetrahydrocannabinol (THC) in polymer-based transmucosal systems. THC was incorporated in polyethylene oxide and hydroxypropylcellulose matrices by a hot-melt fabrication procedure, utilizing various processing aids. The chemical stability of the drug in the polymeric matrices was investigated with respect to processing temperature, processing time, formulation additives, and storage conditions. HPLC analysis of the THC-loaded systems indicated that the extent of drug degradation was influenced by all of the above mentioned variables. THC was particularly unstable in the vitamin E succinate-processed films, indicating a potential incompatibility. Thermal stability of the drug, polymers, and other ingredients at the elevated processing temperatures during the fabrication procedure, was evaluated using the isothermal mode of thermo-gravimetric analysis. When held at 160 and 200°C, the weight percentage of THC decreased linearly as a function of time. Weight loss was controlled by blending the drug with polymers, PEO and HPC, of which PEO was determined to be more effective. Although higher temperatures lowered the polymer melt viscosity, THC and other materials were chemically and thermally unstable at such high temperatures. Due to this, matrix fabrication was found to be favorable at relatively lower temperatures, such as 120°C.