Hydrotropic solubilisation

Applications. The short chain ADPODS products, usually C6, are effective hydrotropes. They are able to significantly reduce the viscosity of LAS-based formulations and to solubilise up to 25% octanol in water. The ADPODS hydrotropes are more efficient than short chain alkylbenzenes (such as toluene and xylene sulphonates) but are significantly more expensive. 

Etman, M.A. Nada, A.H. Hydrotropic and cosolvent solubilisation of indomethacin. Acta Pharm. 1999, 49, 291-298. 

Pharmaceutical solutions might appear to be extremely simple systems, but it is in the solution state that degradation takes place most rapidly, and the solubilisation of poorly soluble compounds is often very difficult. It is ideal if a dmg can be formulated as a simple stable aqueous solution when required for injection, but resort to additives such as water-miscible solvents and surfactants, hydrotropes and cyclodextrins to increase the water solubility of the drug complicates the formulation. Here we deal with simple solutions. Some of the special problems related to peptide and protein solubility are discussed in Chapter 11. 

Coupling agent (co-solvent, hydrotrope or solubiliser) (%) GC, HPLC or column chromatography... 

The ability to solubilise hydrophobic compounds in water starts at a concentration named Minimum Hydrotropic Concentration (MHC), ° which is usually high, up to more than 1 mol/L, depending on the nature of the lipophilic part of the hydrotrope (see Table 2). This concentration at which hydrotropic properties starts expressing is usually also the concentration at which several properties in solution change (surface tension, viscosity, self-diffusion, etc.., ). ... 

Table 2 Minimum Hydrotropic Concentrations (MHO of various hydrotropes determined by solubilisation of a hydrophobic dye in water or surface tension measurements (indicated by ). For the solvo-surfactants (liquids at room temperature), T9o% determined by ATG (see text) is also given. ...

Fig. 10 Schematic representation the solubilisation of a hydrophobic compound in water by hydrotrope and surfactant solutions. CMC = Critical Micellar Concentration, MHC = Minimum Hydrotropic Concentration.

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