The aim of the present study was to fabricate spontaneous emulsifying powders (SEP) for improving dissolution of poorly water-soluble drugs for oral drug delivery. The effect of drugs with different lipophilicity (logP), that is, nifedipine, felodipine, manidipine, and itraconazole on crystalline properties and dissolution profiles of SEP was also examined. The liquid spontaneous emulsifying formulation (SEF), composing of polyoxyl 35 castor oil, caprylic/capric glyceride and diethylene glycol monoethyl ether at a ratio of 1:1:8, was solidified with three different solid carriers, namely, fumed silica, porous silicon dioxide and porous calcium silicate (at 20%-50%). Porous calcium silicate at a concentration of 50% produced an excellent solid SEP formulation with the highest drug dissolution. The SEP formulations were free flowing with similar characteristics as that of liquid SEF. The differential scanning calorimetry and powder X-ray diffraction studies revealed the transformation of crystalline drugs (in pure drugs) to amorphous drugs (in the SEP formulations). This was further confirmed by scanning electron microscopy. Also, SEP containing 50% porous calcium silicate significantly improved the dissolution rate of all drugs tested due to the fast spontaneous emulsion formation and the decreased droplet size. Accordingly, this novel SEP formulation is the versatile and useful formulation that could be used to enhance the oral bioavailability of drugs by improving the dissolution of poorly water-soluble drugs. (C) 2014 Elsevier B.V. All rights reserved.