Formulation Using Hansen Solubility Parameters

Hansen Solubility Parameters (HSP) were published by Dr. Hansen in 1967. The energy related to solubility between molecules is divided into three terms: dispersion term, polarization term, and hydrogen bonding term. The three terms are regarded as a three-dimensional vector. Solubility is determined according to the similarity of the vectors. HSP can be used to determine how much of a compound (drug) is soluble in a given solvent. Here, I will explain how to use HSP as a measure of solubility in pharmaceutical formulations. When synthesizing a pharmaceutical product, a mixture of various by-products is produced in addition to the target drug. In order to purify them and obtain the target substance, extraction, distillation, and sublimation techniques are required. Since these technologies are separation and purification methods based on differences in solubility, the HSP concept is useful. In addition, recent pharmaceuticals have larger molecules and lower solubility. Therefore, crystallization is controlled using HSP. Interactions with cyclodextrins and polymers are being predicted from HSP.