Introduction:

Solubility studies and obtaining physicochemical data on drugs in pure solvents belonging to different chemical classes are key to developing new drug formulations. In this work, Hansen partial solubility parameters (HSP) were calculated to assess the miscibility and intermolecular interactions of barnidipine in seventeen pure solvents. The comparison of the results obtained with the theoretical values calculated according to the structure of barnidipine, were valuable to analyse the influence of the solute-solute, solute-solvent relationships of the additive contribution groups, on the chemical and physical properties of this molecule with the solvents of different polarity tested, to provide relevant information highly useful in the pharmaceutical industry.

Method:

Equilibrium barnidipine solubilities in mono-solvents was determined using the classical shake-flask method, followed by UV-spectrophotometric analysis at 298.15 K. The partial solubility parameters were calculated by applying theoretical group contribution methods, proposed by Hoftyzer-Van Krevelen and Fedors. The KAT-LSER model was used to investigate the effect of solvent based on the concept of linear solvation energy relationships. The mole fraction was obtained from the densities of the solutions. Solid-phase analyses were made by calorimetry differential scanning.

Results:

The modification introduced in the extended Hansen method, that is, the use of lnX2 as the dependent variable, provided excellent results. The highest solubility values have been found in polar solvents. It is observed that solvent-solvent and solute-solvent intermolecular interactions through hydrogen bonds and van der Waals forces, significantly influence drug solubility.

Conclusions:

The affinity between barnidipine and each one of the selected solvent was evaluated by using HSP. Results showed that HSP could be well used to analyse drug solubility in particular solvents. Barnidipine is easier to dissolve in solvents with shorter carbon chains and higher polarity.

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