Model aqueous dispersions of isopropylantipyrine, solvent deposited on hydrophilic organic polymer carriers

The known solvent deposition technique was modified using aqueous soluble organic polymer carriers solvated with 1,2-propylenglycol in order to prepare sorbates which can be easily transformed ex tempore in aqueous dispersions. Sorbates of the model drug isopropylantipyrin (IPrA) were developed with methylcellulose (MC), hydroxypropylcellulose (HPC) and hydroxypropylmethylcellulose (HPMC) in drug/polymer ratios from 1:0.5 up to 1:4 (w/w). The effect of the hydrophilic carriers on the properties of model ex tempore prepared 0.5% aqueous dispersions of the corresponding sorbates was evaluated. It was established that all sample preparations are physically stable homogenious dispersions with a very good redispersibility. The 1:2 and 1:4 sorbate preparations are structural pseudoplastic systems without thixotropy and their viscosity does not significantly differ from the viscosity of the pure polymer solutions. Besides, the samples with MC show a higher viscosity. It was also established that the hydrophilic carriers moderately increase (with about 12-20%) the IPrA aqueous solubility in the ex tempore prepared model aqueous dispersions. Their effect is more pronounced on the in vitro drug release rate and extent. But, in all cases the final drug amount released was smaller than the drug amount dissolved. Some drug/polymer interactions can be assumed which are more pronounced with the solvated MC carrier. Moreover, the final amount IPrA released from the corresponding 1:2 sorbate with MC in comparison to the other polymers was about 2 times smaller. The favourable properties of the IPrA/MC 1:2 sorbate aqueous dispersion can be a basis for further investigations to formulate drug systems with a modified release.