SATURATION SOLUBILITY OF SCOPOLAMINE IN THIN FILMS OF POLYACRYLATE PRESSURE SENSITIVE ADHESIVES IS TEMPERATURE DEPENDENTAbstract
The method of drug uptake from solid solution has been used to measure the saturation solubility of scopolamine base in various pressure sensitive adhesive DURO-TAKs at elevated temperature. The saturation solubility was strongly temperature dependent, being 50 – 100 % larger at 45°C than at 25°C. The higher temperature also caused much more rapid approach to equilibrium distribution of the drug between donor, separating membrane, and acceptor layers. With a cross-linked DURO-TAK 87-2677 the saturation solubility is 10.7 ± 0.30 % (n=4) at 25 °C, rising to 16.5 ± 0.54 % at 45 °C (n=4). The non-cross-linked DURO-TAK 87-4098 gives lower values of 6.3 ± 0.27% w/w(n=4) at 25 °C, rising to 13.2 ± 1.14 % at 45 °C. The hydrophobic DURO-TAK 87-2510gives the lowest values of 4.2 ± 0.17 % w/w (n=4) at 25 °C and 8.7 ± 0.45 % (n=4) at 45°C. The thermodynamic activity of the drug in the thin polymer film will therefore decrease as temperature increases.