Sulfonamides are drugs extensively used for treatment of different infections caused by several Gram-negative and Gram-positive bacteria as well as by some fungi. Drugs biodisponibility is influenced for several physicochemical properties of drugs and aqueous media. Thus, transfer properties involving dissolution and permeation are crucial for understanding of release and absorption of drugs after enteral administration. For these reasons, in this research the molar dissolution enthalpies (Δsoln H) of sodium sulfadiazine (NaSD), sodium sulfamerazine (NaSMR) and sodium sulfamethazine (NaSMT) were determined as a function of concentration and temperature in water and normal saline solution (NSS, NaCl 0.9% m/m in water) by using an isoperibolic calorimeter. From these values, the standard dissolution enthalpies (ΔsolnH°) were calculated in both solvent systems for the three sodium sulfonamides studied. In addition, the standard enthalpies of the transfer process of sodium sulfonamides from water to NSS were also determined. ΔsolnH values of NaSD and NaSMR in water and in NSS indicate that the dissolution processes for these solutes are endothermic in nature. For NaSMT, the dissolution process is exothermic at low temperatures and endothermic at high temperatures, which is related to the hydration process of hydrophobic molecules. The presence NaCl, which acts as a structure disruptor for water, raises the energy required for solvent molecules to rearrange around ions, leading to more positive standard enthalpies in NSS at low temperatures. Likewise, in NSS and at high temperatures solute–cosolute interactions are favored, which leads to lower ΔsolnH° values in the presence of NaCl. The heat capacities of solution (ΔsolnC<Stack> P ° </Stack>) signs are positive for all three sodium sulfonamides in both water and NSS, indicating the water structure-forming behavior of these solutes. The greater ΔsolnH°-dependence on the temperature observed for NaSMT suggests a greater hydrophobic character for this solute, which is consistent with the greater hydrophobic surface owing two additional –CH3 groups in its structure. Positive values of transfer enthalpies (ΔtrH°) are related to the hydrophobicity of the solutes, and negative values indicate a favoring of solute–cosolute electrostatic type interactions, which are strengthened at high temperatures. Thus, this research demonstrated the main role of hydrophobic effects on the dissolution of these compounds.

Molar dissolution enthalpies of some sodium sulfonamides in water and normal saline solution at several temperatures

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2025年3月1日

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Gerson A. Rodríguez,
Fleming Martínez,
Edgar F. Vargas

摘要

Sulfonamides are drugs extensively used for treatment of different infections caused by several Gram-negative and Gram-positive bacteria as well as by some fungi. Drugs biodisponibility is influenced for several physicochemical properties of drugs and aqueous media. Thus, transfer properties involving dissolution and permeation are crucial for understanding of release and absorption of drugs after enteral administration. For these reasons, in this research the molar dissolution enthalpies (Δ_soln H) of sodium sulfadiazine (NaSD), sodium sulfamerazine (NaSMR) and sodium sulfamethazine (NaSMT) were determined as a function of concentration and temperature in water and normal saline solution (NSS, NaCl 0.9% m/m in water) by using an isoperibolic calorimeter. From these values, the standard dissolution enthalpies (Δ_solnH°) were calculated in both solvent systems for the three sodium sulfonamides studied. In addition, the standard enthalpies of the transfer process of sodium sulfonamides from water to NSS were also determined. Δ_solnH values of NaSD and NaSMR in water and in NSS indicate that the dissolution processes for these solutes are endothermic in nature. For NaSMT, the dissolution process is exothermic at low temperatures and endothermic at high temperatures, which is related to the hydration process of hydrophobic molecules. The presence NaCl, which acts as a structure disruptor for water, raises the energy required for solvent molecules to rearrange around ions, leading to more positive standard enthalpies in NSS at low temperatures. Likewise, in NSS and at high temperatures solute–cosolute interactions are favored, which leads to lower Δ_solnH° values in the presence of NaCl. The heat capacities of solution (Δ_solnC _P ^° ) signs are positive for all three sodium sulfonamides in both water and NSS, indicating the water structure-forming behavior of these solutes. The greater Δ_solnH°-dependence on the temperature observed for NaSMT suggests a greater hydrophobic character for this solute, which is consistent with the greater hydrophobic surface owing two additional –CH₃ groups in its structure. Positive values of transfer enthalpies (Δ_trH°) are related to the hydrophobicity of the solutes, and negative values indicate a favoring of solute–cosolute electrostatic type interactions, which are strengthened at high temperatures. Thus, this research demonstrated the main role of hydrophobic effects on the dissolution of these compounds.