The low bioavailability of highly hydrophobic drugs with extremely low water solubility can be a serious problem. Different approaches have been attempted to reach desired level of drug solubility and dissolution rate. Such approaches are based on the using of preparations with increased surface area (micronised powders), inclusion complexes (cyclodextrins and derivatives), co-precipitates with water-soluble polymers (PEG, Poloxamer, PVP, HPMC) and non-electrolytes (urea, mannitol, sugars etc.), micellar solutions in surfactant systems (Cremophor~TM, Poloxamers~TM, Tweens~TM, Gellucires~TM), multilayer vesicles (liposomes and niosomes), emulsions, microemulsions and self-emulsifying compositions. Most of these procedures are quite effective for bioavailability improvement of immediate drug release formulations.
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