Effect of sodium chloride on the gelation temperature, gel strength and bioadhesive force of poloxamer gels containing diclofenac sodium

Liquid suppository systems composed of poloxamers and bioadhesive polymers were easy to administer to the anus and mucoadhesive to the rectal tissues without leakage after the dose. However, a liquid suppository system contai ning diclofenac sodium could not be developed using bioadhesive polymers, s ince the drug was precipitated in this preparation. To develop a liquid sup pository system using sodium chloride instead of bioadhesive polymers, the physicochemical properties such as gelation temperature, gel strength and b ioadhesive force of various formulations composed of diclofenac sodium, pol oxamers and sodium chloride were investigated. The mixtures of P 407 (15%) and P 188 (15-20%) existed as a liquid at room temperature, but gelled at p hysiological temperature. Diclofenac sodium significantly increased the gel ation temperature and weakened the gel strength and bioadhesive force, whil e sodium chloride did the opposite. Furthermore, the poloxamer gels with le ss than 1.0% of sodium chloride, in which the drug was not precipitated, we re inserted into the rectum of rabbits without difficulty and leakage, and retained in the rectum of rats for at least 6 h. Our results suggested that a thermosensitive liquid suppository system with sodium chloride and polox amers was a more physically stable and convenient rectal dosage form for di clofenac sodium. (C) 2001 Elsevier Science B.V. All rights reserved.