SURFACE MODIFICATION OF WATER-INSOLUBLE DRUG PARTICLES WITH STARCH

Paranterally applied, water-insolubile drug-particles are better toler ated if the a) particle surface is hydrophil enough, b) surface-charge (measured as zeta-potential) in physiological liquids does not exceed +8mV resp. -8mV. It is possible to coat lipophilic drug-particles wit h a thin - hydrophilic - amylosefilm by a new, only temperature-contro lled setback - (= retrogradation) - technique. Thus, it is not necessa ry to use any unphysiological agents such as monomers or organic solve nts. 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 invest igated tapioca starches (Mai zena #A6, T-R 61 degrees C). Starches wit h higher set-back-temperature (cave: particle growth), e.g. lentil-and plantains starch (T-R 94 degrees C) are not recommended. Potato starc hes (Sudstarke, Roquette, Emsland, Klenk) do not retrograde at lowerin g temperature. Therefore, these starches are not usable for the invest igated set-back-method. Amylose coated particles show not only optimal surface-charge, but also a reduced sedimentation-velocity, caused by an enlarged hyrodynamic-diameter.