of the hydrophobic effect. Thomas and Seelig [397] found the partitioning of the Ca2+ antagonist, flunarizine (a weak base), also to be predominantly enthalpy-driven, with AHte —22.1 kJ mol—\ again at odds with the established ideas of entropy-driven partitioning of drugs. The same surprise was found for the partitioning of paclitaxil [398]. These observations thus appear to suggest that drugs partition into membrane phases because they are lipophilic, and not because they are hydro-phobic! This needs to be investigated more extensively, using microcalorimetry.

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