The application of many recently developed or approved drugs and pharmaceuticals is seriously hampered by their low solubility in aqueous media. Hence, numerous promising pharmaceutical delivery systems (including novel "smart" systems based on poloxamer gels, which have highly advantageous thermo-reversible characteristics and low toxicity) cannot solubilize required doses of various drugs without additives such as co-solvents or salts. Therefore, we have studied the effects of dimethyl sulphoxide (DMSO)-a commonly used co-solvent during drug development stages-on the micellization, gelation and dissolution properties of aqueous poloxamer solutions. Differential scanning calorimetry and tube inversion experiments clearly showed that DMSO induces reductions in the critical micellization and gelation temperatures of poloxamer systems. In addition, high resolution solid state ¹H Magic Angle Spinning Nuclear Magnetic Resonance (MAS NMR) analyses provided indications of the specific chemical groups in the poloxamer affected by DMSO, and the molecular mechanism involved. The presence of DMSO accelerated dissolution of the pure gel in water and the release of a hydrophobic drug (flufenamic acid) from poloxamer gel, while it reduced the release of a hydrophilic drug (metoprolol tartrate).

A method for the in situgelation of poloxamers and the mucoadhesive polymer chitosan has been developedby exploiting the tendency of poloxamer solution to form gel at physiological temperatures and of chitosan (CT) to form ionotropic gel structures in the presence of sodium tripolyphosphate (TPP). Novel poloxamer gels containing CT –TPP complex formed in situduring the administration were prepared bymixing poloxamer –CT and poloxamer–TPPsolutions in double syringes. The micellization and gelation ofpoloxamer 407 in the presence of chitosan and/or TPP were studied using differential scanning calorimetry and tube inversion; both additives were found to reduce the critical micellization temperature and critical gelation temperature of poloxamer aqueous solution. The poloxamer gels  ontaining CT –TPPcomplexformed in situwere found to exhibit reduced dissolution rate and superior release characteristicswith three different drugs –metoprolol, doxycycline and flufenamic acid. Furthermore, by varying thecompositions of the two solutions independently, it is possible to control the pH in a way to suit the solubilization of a drug as well as the specific environment of a particular application site. By varying the concentrations of chitosan, TPP and poloxamer, the delivery system can be fine-tuned to afford gels with specific properties, ranging from nanoparticle suspensions to semisolid gels. These in situgels have thepotential to increase the utility of thermo-reversible poloxamers in drug delivery

Bacterial virulence inhibitors are potential novel drugs that may be used to treat infections. N′-(3,5-dibromo-2-hydroxy-benzylidene)-nicotinic acid hydrazide, ME0052, has been shown to inhibit type III secretion (T3S) and virulence in several Gram-negative enteric pathogens including Yersinia pseudotuberculosis. In vitro data suggest that ME0052 may be developed into drugs against bacterial gastroenteritis. Here we describe preliminary pharmacokinetics of ME0052 after intraperitoneal and subcutaneous administration in mice. The aim of this work was to identify suitable formulations and to determine pharmacokinetic parameters prior to testing in animal infection models. Peak plasma concentrations above the IC50 for virulence inhibition were achieved with high dose formulations and the elimination half-life was prolonged from 0.5 to 3.4 h using a poloxamer 407-based slow-release formulation.