Revisiting the Total Hildebrand and Partial Hansen Solubility Parameters of Analgesic Drug Meloxicam

Abstract

The reported total Hildebrand solubility parameter (δ2) value of meloxicam, as calculated based on the group contribution method proposed by Fedors, was compared with those estimated based on the maximum solubility peaks observed in different aqueous cosolvent systems at T = 298.15 K. Thus, the observed δ2 values varied from (19.8 to 29.1) MPa1/2, respectively. Moreover, the Hansen solubility parameters (HSPs) and the total Hildebrand solubility parameter were also determined by using the Bustamante regression method with the reported experimental solubility values of meloxicam in 31 neat solvents (30 organic solvents and water), obtaining the values: δd = 19.9 MPa1/2, δp = 16.9 MPa1/2, δh = 5.7 MPa1/2, and δT = 26.7 MPa1/2. Furthermore, the HSPs of meloxicam were also estimated based on the Hoftyzer–van Krevelen group contribution method, obtaining the values: δd = 17.9 MPa1/2, δp = 20.3 MPa1/2, and δh = 9.2 MPa1/2, and the total solubility parameter as: δT = 28.6 MPa1/2. In addition, the Kamlet–Abboud–Taft linear solvation energy relationship (KAT-LSER) model was also employed to evaluate the role of different intermolecular interactions on the dissolution of meloxicam in different solvents that varied in terms of polarity and hydrogen bonding capability.