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Spray-Drying, Solvent-Casting and Freeze-Drying Techniques: a Comparative Study on their Suitability for the Enhancement of Drug Dissolution Rates



Solid dispersions (SDs) represent the most common formulation technique used to increase the dissolution rate of a drug. In this work, the three most common methods used to prepare SDs, namely spray-drying, solvent-casting and freeze-drying, have been compared in order to investigate their effect on increasing drug dissolution rate.


Three formulation strategies were used to prepare a polymer mixture of polyvinyl-alcohol (PVA) and maltodextrin (MDX) as SDs loaded with the following three model drugs, all of which possess a poor solubility: Olanzapine, Dexamethasone, and Triamcinolone acetonide. The SDs obtained were analysed and compared in terms of drug particle size, drug-loading capacity, surface homogeneity, and dissolution profile enhancement. Physical-chemical characterisation was conducted on pure drugs, as well as the formulations made, by way of thermal analysis and infrared spectroscopy.


The polymers used were able to increase drug saturation solubility. The formulation strategies affected the drug particle size, with the solvent-casting method resulting in more homogenous particle size and distribution when compared to the other methods. The greatest enhancement in the drug dissolution rate was seen for all the samples prepared using the solvent-casting method.


All of the methods used were able to increase the dissolution rate of the pure drugs alone, however, the solvent-casting method produced SDs with a higher surface homogeneity, drug incorporation capability, and faster dissolution profile than the other techniques.

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Heat capacity


Active pharmaceutical ingredients


Biopharmaceutical classification systems


Dimethyl sulfoxide


Differential scanning calorimetry




Dulbecco buffer phosphate


Fourier transform infrared


Hot melt extrusion




Potassium bromide








Solid dispersion


Scanning electron microscopy analysis


Glass transition


Thermogravimetric analysis


Melting point


Triamcinolone acetonide




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Correspondence to Mariano Licciardi.

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De Mohac, L.M., Caruana, R., Cavallaro, G. et al. Spray-Drying, Solvent-Casting and Freeze-Drying Techniques: a Comparative Study on their Suitability for the Enhancement of Drug Dissolution Rates. Pharm Res 37, 57 (2020).

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Key Words

  • dissolution rate
  • freeze-drying
  • solid dispersion
  • solvent-casting method
  • spray-drying