Solubility of Ketoconazole in Polyethylene Glycol 200 + Water Mixtures at 298.2–318.2 K

Comparative Drug Solubility Studies Using Shake-Flask Versus a Laser-Based Robotic Method

Drug solubility is of central importance to the pharmaceutical sciences, but reported values often show discrepancies. Various factors have been discussed in the literature to account for such differences, but the influence of manual testing in comparison to a robotic system has not been studied adequately before. In this study, four expert researchers were asked to measure the solubility of four drugs with various solubility behaviors (i.e., paracetamol, mesalazine, lamotrigine, and ketoconazole) in the same laboratory with the same instruments, method, and material sources and repeated their measurements after a time interval. In addition, the same solubility data were determined using an automated laser-based setup. The results suggest that manual testing leads to a handling influence on measured solubility values, and the results were discussed in more detail as compared to the automated laser-based system. Within the framework of unavoidable uncertainties of solubility testing, it is a possibility to combine minimal experimental testing that is preferably automated with mathematical modeling. That is a practical suggestion to support future pharmaceutical development in a more efficient way.

Thermodynamic Analysis of the Solubility of Isoniazid in (PEG 200 + Water) Cosolvent Mixtures from 278.15 K to 318.15 K

The solubility of drugs in cosolvent systems of pharmaceutical interest is of great importance for understanding and optimizing a large number of processes. Here, we report the solubility of isoniazid in nine (PEG 200 + water) cosolvent mixtures at nine temperatures (278.15, 283.15, 288.15, 293.15, 298.15, 303.15, 308.15, and 318.15 K) determined by UV-vis spectrophotometry. From the solubility data, the thermodynamic solution, mixing, and transfer functions were calculated in addition to performing the enthalpy-entropy compensation analysis. The solubility of isoniazid depends on the concentration of PEG 200 (positive cosolvent effect) and temperature (endothermic process) reaching its maximum solubility in pure PEG 200 at 318.15 K and the lowest solubility in pure water at 278.15 K. The solution process is favored by the solution entropy and according to the enthalpy-entropy compensation analysis it is driven by entropy in mixtures rich in water and by enthalpy in mixtures rich in PEG 200.

Experimental Solubility of Ketoconazole, Validation Models, and In vivo Prediction in Human Based on GastroPlus

The study aimed to identify a suitable cosolvent + water mixture for subcutaneous (sub-Q) delivery of ketoconazole (KETO). The solubility was assessed for several dimethyl acetamide (DMA) + water mixtures at T = 293.2 to 318.2 K and pressure P = 0.1 MPa. The experimental solubility (x_e) was validated using the Van 't Hoff and Yalkowsky models and functional thermodynamic parameters (enthalpy Δ_solH°, entropy Δ_solS°, and Gibbs free energy Δ_solG°). The in vitro drug release study was performed at physiological pH, and the data served as the input to GastroPlus, which predicted the in vivo performance of KETO dissolved in a DMA + water cosolvent mixture for sub-Q delivery in human. The maximum solubility (mole fraction) of KETO (9.81 × 10^-1) was obtained for neat DMA at 318.2 K whereas the lowest value (1.7 × 10^-5) was for pure water at 293.2 K. An apparent thermodynamic analysis based on x_e gave positive values for the functional parameters. KETO dissolution requires energy, as evidenced by the high positive values of Δ_solH° and Δ_solG°. Interestingly, Δ_solG° progressively decreased with increasing concentration of DMA in the DMA + water mixture, suggesting that the DMA-based molecular interaction improved the solubilization. Positive values of Δ_solG° and Δ_solS° for each DMA + water cosolvent mixture corroborated the endothermic and entropy-driven dissolution. GastroPlus predicted better absorption of KETO through sub-Q delivery than oral delivery. Hence, the DMA + water mixture may be a promising system for sub-Q delivery of KETO to control topical and systemic fungal infections.

Thermodynamic, Computational Solubility Parameters in Organic Solvents and In Silico GastroPlus Based Prediction of Ketoconazole

The study aimed to select a suitable solvent capable to solubilize ketoconazole (KETO) and serve as a permeation enhancer across the skin. Experimental solubility and Hansen solubility parameters were obtained in ethanol, dimethyl sulfoxide (DMSO), ethylene glycol, oleic acid, span 80, limonene, eugenol, transcutol (THP), labrasol, and propylene glycol. Thermodynamic functional parameters and computational models (van't Hoff and Apelblat) validated the determined solubility in various solvents at T = 298.2 K to 318.2 K and P = 0.1 MPa. The HSPiP software estimated the solubility parameters in the solvents. The maximum mole fractional solubility values of KETO were found to be in an order as oleic acid (8.5 × 10-3) > limonene (7.3 × 10-3) > span 80 (6.9 × 10-2) > THP (4.9 × 10-2) > eugenol (4.5 × 10-3) at T = 318.2 K. The results of the apparent thermodynamic analysis confirmed that the dissolution rate was endothermic and entropy driven. The GastroPlus program predicted significantly high permeation of KETO (79.1%) in human skin from the KETO-THP construct as compared to drug solution (38%) and excellent immediate release from THP-solubilized construct (90% < 1 h). Hence, THP could be a better option for topical, transdermal, and oral formulation.