• Poloxamer-polysaccharide composites gave prolonged drug release of local anesthetics • Alginate was superior to chitosan and hyaluronate • The concentration of alginate was critical, above 0.5% the positive effect diminished • Prolonged drug release was due to reduced initial burst effect and reinforced structure • Release of local anesthetics was longer than the expected postoperative recovery time Poloxamers are popular in controlled drug delivery due to the simplicity of the concept of thermoresponsive in situ gelling. However, formulation is challenged by difficulties in attaining a resistant structure, as well as preventing the initial burst release of the drug. In this work, the challenge was addressed by preparing physical composites with polysaccharides. Poloxamers (c tot 20%) were combined with alginate, chitosan, or hyaluronate (0.5%), with the purpose of revealing the potential synergism in prolonging the release of local anesthetics, i.e. lidocaine and ropivacaine hydrochloride. Alginate was identified as the polysaccharide with the greatest potential to prolong the drug release. The experimental outcome was shown to be dependent on alginate concentration; above the critical value of 0.5% the beneficial effect started to diminish. Rheological characterization demonstrated that alginate ≤0.5% also facilitated the sol-gel transition of poloxamers, while maintaining the formulation injectability. Finally, another drug release study was performed in which the amount of the release medium was reduced to emulate the in vivo conditions encountered during performance of a peripheral nerve block. Drug release extending over 5 days, as observed for alginate 0.25%, was considered convenient in view of the typical recovery time in this type of surgery.
Ćuk et al. (Fri,) studied this question.