Surface modification of water-insoluble drug particles with starch

Parenterally applied, water-insolubile drug-particles are better tolerated if the (a) particle surface is hydrophil enough, (b) surface-charge (measured as zeta-potential) in physiological liquids does not exceed +8mV resp. -8mV. Itis possible to coat lipophilic drug-particles with a thin - hydrophilic - amylosefilm by a new, only temperature-controlled setback - (= retrogradation) - technique. Thus, it is not necessary to use any unphysiological agents such as monomers or organicsolvents. This process requires starches with low set-back-temperature (TR), e.g. Schneeapfel - (T-R 49 degrees C), banana (plantains) - (T-R 54 degrees C) and chickpea starch (T-R 55 degrees C) or one of the investigated tapioca starches (Mai zena A6,T-R 61 degrees C). Starches with higher set-back-temperature (cave: particle growth), e.g. Lentil-and plantains starch (T-R 94 degrees C) are not recommended. Potato starches (Sudstarke, Roquette, Emsland, Klenk) do not retrograde at lowering temperature. Therefore, these starches are not usable for the investigated set-back-method. Amylose coated particles show not only optimal surface-charge, but also a reduced sedimentation-velocity, caused by an enlarged hyrodynamic-diameter.