Hydrophilic polymer solubilization on norfloxacin solubility in preparation of solid dispersion

The effects of single and binary hydrophilic polymers on the solubility and dissolution parameters of a poorly water-soluble drug, norfloxacin, via solid dispersions using the solvent evaporation method were investigated. Polyvinylpyrrolidone (PVP) was soluble, hydroxypropyl cellulose-low substituted (HPC-L) was partially soluble and polyacrylic acid (Carbopol) was insoluble in the solvent, acetone. All the single hydrophilic polymer dispersions increased the solubility and dissolution rate of norfloxacin. Norfloxacin/HPC-L solid dispersion demonstrated the highest solubility and dissolution, followed by norfloxacin/PVP and norfloxacin/Carbopol dispersions. The use of binary polymers PVP/HPC-L further enhanced the solubility and dissolution of norfloxacin. On the contrary, binary polymers PVP/Carbopol and HPC-L/Carbopol did not show a similar enhancement. The FTIR spectrum of norfloxacin/PVP/HPC-L showed no chemical interaction between the drug and polymers. DSC thermogram exhibited a reduction in intensity and enthalpy of the drug peak. Disappearance of norfloxacin peak and reduction in crystallinity was observed in XRD analysis. In conclusion, for the enhancement of the solubility and dissolution rate of a poorly water-soluble drug, it is important for the single or binary hydrophilic polymers to be partially soluble during the solvent evaporation method. The polymer not only improves the wetting of the drug but also provides a surface area for drug adsorption, modifying the solid state property of the drug.