Buccal delivery system of active pharmaceutical ingredients-ionic liquid (API-IL): Effects of API-IL loading and gelatin film concentration

Ionic liquid (IL) salt of active pharmaceutical ingredient (API) represents a promising formulation strategy to address low drug solubility and polymorphism prevalent in API solid crystals. The present work developed for the first time a buccal delivery system of API-IL via fast-dissolving API-IL-loaded gelatin films. Imidazolium-based ibuprofen salt was used as the model API-IL. The effects of API-IL loading and gelatin concentration on the film's (i) mechanical strength, (ii) inter-batch uniformity in the films’ API payload, weight, and thickness, (iii) thermal stability, (iv) API dissolution and solubility enhancement were investigated. The plasticizer role of API-IL was evident, where minimum 30 wt% API-IL loading was needed to produce flexible yet mechanically-strong films. Lower API-IL loading produced brittle films due to insufficient plasticization facilitated by hydrogen bond interactions between API-IL and gelatin. Gelatin concentration influenced films’ mechanical strength, weight/thickness, and API dissolution rate. Depending on the API-IL loading and gelatin concentration, films with API payload (7–30 mg/cm²), thickness (300–900 µm), and weight (20–110 mg/cm²) were produced at nearly 100% efficiency and high inter-batch uniformity. API-IL existed as amorphous liquid in the film exhibiting fast API dissolution (100% in 15 min) and high kinetic solubility (8 times thermodynamic solubility) in simulated saliva fluid.