Lyophilized muco-adhesive wafers with optimum drug loading for potential buccal delivery have been developed. A freeze-annealing cycle was used to obtain optimized wafers from aqueous gels containing 2% κ-carrageenan (CAR 911), 4% pluronic acid (F127), 4.4% w/w polyethylene glycol with 1.8% w/w paracetamol or 0.8% w/w ibuprofen. Thermogravimetric analysis showed acceptable water content between 0.9 -1.5%. Differential scanning calorimetry and X-ray diffraction showed amorphous conversion for both drugs. Texture analysis showed ideal mechanical and mucoadhesion characteristics whilst both drugs remained stable over six months and drug dissolution at a salivary pH showed gradual release within two hours. The results show the potential of CAR 911 and F127 based wafers for buccal mucosa drug delivery.Keywords: Amorphous, Buccal drug delivery system, Carrageenan, Dissolution characteristics, Lyophilized wafer, (Muco)-adhesion, 3
IntroductionMucosal drug delivery systems have many advantages such as bypassing first pass liver metabolism and avoiding GI enzymatic degradation. Drug absorption via the buccal mucosa surface and into the systemic circulation is relatively fast (compared to the skin) owing to the highly vascularized structure underneath the mucosal tissues [1,2].Lyophilisation has been used in pharmaceutical industries to improve the stability of formulations. The investigation of fundamental physical phenomena occurring during each step of freeze drying has enabled formulators to produce stable and well-designed freezedried pharmaceutical dosage forms [3]. Freeze dried products do not necessarily need to be refrigerated and can be stored at ambient temperatures. This will be favourable for labile drugs including vaccines and proteins [4].Lyophilisation comprises a freezing step where ice crystals form and the solute becomes extremely concentrated. As the temperature falls below the glass transition temperature (T g ), the system is changed into a viscous glass. Incomplete crystallization may, however, lead to sample collapse or formation of mixtures of different polymorphic forms that causes problems in characterization and manufacturing reproducibility. Frozen products can be categorized as either crystalline or amorphous glass in structure. Crystalline products have a distinct "eutectic" freezing/melting point which is referred to as the collapse temperature. Amorphous products have a corresponding "glass transition" temperature and they are much more difficult to freeze-dry. Even though most materials that are freeze dried are actually amorphous, the term "eutectic" is often used to define the freezing/melting point of sample [4].To optimise the process of solute crystallization during freezing, thermal treatment, or "annealing", will be advantageous. Annealing is the process of heating a sample above its 4 glass transition temperature (but below the eutectic and/or ice melting temperature) and allowing the glass to relax and crystallize. Metastable glass formation is possible depending on the f...