Mechanistic insights of the controlled release properties of amide adhesive and hydroxyl adhesive.

Although interactions between drugs and acrylate pressure sensitive adhesives (PSAs) containing amide groups were reported in the previous studies, detailed studies elucidating their mechanism of action are still lacking. In the present study, an amide PSA (AACONH) and a hydroxyl PSA (AAOH, as the control) were synthesized, and their molecular mechanism of controlled drug release was described. Using zolmitriptan (ZOL) and etodolac (ETO) as model drugs, in vitro drug release and skin permeation experiments were performed. Intermolecular interactions between drugs and PSAs were determined by Flory-Huggins model, FT-IR spectroscopic analysis and molecular modeling. In addition, PSA mobility was evaluated using differential scanning calorimetry and rheology study. Release percent of ZOL and ETO from AACONH were 43.9 ± 0.3% and 50.0 ± 2.0% respectively, while from AAOH, the release percent of ZOL and ETO were 61.4 ± 1.2% and 81.0 ± 1.2% separately. As a consequence of controlled drug release, skin permeation of both drugs was significantly controlled by AACONH. It was demonstrated that AACONH markedly interacted with drugs, especially with ETO, through hydrogen bonding and weak intermolecular forces (e.g. dipole-dipole and van der waals). PSA mobility of AACONH was significantly increased due to drug-PSA interactions. In conclusion, AACONH had stronger controlled release properties compared with AAOH, which was mainly caused by the stronger interactions between amide groups and drugs. The amide PSA synthesized in the present study was a potential sustained-release excipient for transdermal drug delivery system.