RESUMEN
AIMS: In the present study, a valnemulin hydrogen fumarate prodrug was characterized, its stability was compared with valnemulin hydrochloride, and the efficacy was evaluated in Actinobacillus pleuropneumoniae-induced pneumonia in mice. METHOD: Optical microscopy, X-ray powder diffraction, infrared spectroscopy, and hydrogen nuclear magnetic resonance spectroscopy were used to study the physical and chemical properties of the prodrug. The thermal stability was investigated in comparison with valnemulin hydrochloride to improve the preparation process of valnemulin hydrogen fumarate soluble powder and maximize its drug effect. Additionally, the efficacy of valnemulin hydrogen fumarate was evaluated in a challenge-treatment trial in mice using an in vitro antimicrobial susceptibility test. RESULTS: The valnemulin hydrogen fumarate had high crystallinity. After light irradiation for 20 days, valnemulin hydrogen fumarate did not degrade, whereas valnemulin hydrochloride did. These results showed that the valnemulin hydrogen fumarate was stable. At the same dose in drinking water, the valnemulin hydrogen fumarate was more effective than the reference drug (tiamulin fumarate) in an Actinobacillus pleuropneumoniae challenge-treatment trial. CONCLUSION: Valnemulin hydrogen fumarate shows excellent potential for application as a veterinary drug.
RESUMEN
We prepared a polymorphic form of valnemulin hydrogen tartrate (Form I) to overcome the instability and irritating odor of valnemulin hydrochloride that affect its use in the production and application of veterinary drugs. The physicochemical properties of Form I were characterized by scanning electron microscopy, X-ray powder diffraction, infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analysis. The results showed the crystal structure and thermal properties of Form I were very different from those of a commercially available form of valnemulin hydrogen tartrate (Form II). Form I and Form II were more stable than valnemulin hydrochloride after storage under irradiation and high humidity conditions, respectively. The solubility of Form I was 2.6 times that of Form II, and Form I was selected for use in pharmaceutical kinetics experiments in vivo. Compared to valnemulin hydrochloride, after oral administration at a dose of 10 mg/kg in pigs, Form I had similar pharmaceutical kinetic behavior but a slightly higher area under the concentration–time curve from time zero to the last measurable concentration. Consequently, Form I should be suitable for the development of simple formulations and be effective in the clinical application of veterinary drugs.
