The development of effective delivery systems for poorly soluble pharmaceuticals remains a critical challenge in modern pharmaceuticals. This study explores the use of lysozyme, a biopolymer with unique immunological and stabilizing properties, as a matrix for creating amorphous solid dispersions of nalidixic acid, a model hydrophobic antibiotic. By optimizing the composition using differential scanning calorimetry and X-ray powder diffractometry, a range of ratios of protein matrix and active pharmaceutical ingredient was determined in which amorphous solid dispersions are formed. Spray drying was used to produce microspherical particles suitable for inhalation therapy, resulting in particles predominantly 2–5 μm in size, suitable for alveolar deposition. This work demonstrates the potential of protein carriers such as lysozyme not only to enhance solubility and bioavailability but also to provide a synergistic therapeutic effect. The developed strategy for creating a dosage form is promising for improving the pulmonary delivery of other poorly water-soluble drugs while simultaneously reducing the required doses and minimizing side effects.

Obtaining amorphous forms of drugs is one of the ways to increase bioavailability. This is especially important for active pharmaceutical ingredients belonging to class II and IV according to the biopharmaceutical classification. These compounds include the currently widely used fluoroquinolone antibiotics. They have low solubility in water and are therefore typically used as hydrochlorides. The presence of a strong acid and a charged active pharmaceutical ingredient in the drug increases solubility, but can also lead to additional side effects and decreased permeability. One way to improve the properties of active pharmaceutical ingredients is to convert them to amorphous form. In this study, an amorphous form of the fluoroquinolone antibiotic norfloxacin was obtained, its stability was determined, and its solubility was studied. It was shown that the resulting amorphous form has good temporal stability. The optimal models describing the cold crystallization process are the Nakamura and Sbirrazzuoli models. Despite the slower dissolution kinetics compared to the crystalline sample, the amorphous form shows higher equilibrium solubility values. These results can be used in pharmaceutical engineering to produce amorphous forms of active pharmaceutical ingredients and determine their stability.