Exploring solid forms of oxytetracycline hydrochloride.

Area of Science:

• Pharmaceutical Sciences
• Solid-State Chemistry

Background:

• Oxytetracycline hydrochloride, a tetracycline antibiotic, is known for its polymorphic nature, leading to variable oral absorption.
• Lack of robust solid-state characterization and inconsistent nomenclature complicate the identification of raw oxytetracycline hydrochloride materials.

Purpose of the Study:

• To prepare and characterize novel solid forms of oxytetracycline hydrochloride.
• To evaluate the physicochemical and microbiological properties of these identified solid forms.
• To explore the potential of these polymorphs as candidates for drug repositioning.

Main Methods:

• Crystallization of oxytetracycline hydrochloride from isopropyl alcohol, ethanol, and methanol.
• Characterization using solid-state nuclear magnetic resonance (ssNMR), powder X-ray diffraction (PXRD), infrared spectroscopy (IR), thermal analysis (DSC/TGA), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX).
• Solubility determination in aqueous, simulated gastric, and simulated intestinal fluids.
• Microbiological assays against Escherichia coli and Staphylococcus aureus.

Main Results:

• Successfully prepared and identified four distinct solid forms of oxytetracycline hydrochloride: three stable and one metastable.
• Comprehensive physicochemical characterization confirmed the unique nature of each solid form.
• All identified polymorphs demonstrated comparable antimicrobial efficacy against tested bacterial strains.

Conclusions:

• The characterized solid forms of oxytetracycline hydrochloride offer distinct physicochemical profiles.
• The consistent antimicrobial activity across polymorphs supports their potential for drug repositioning strategies.
• Further research into these solid forms could lead to novel therapeutic alternatives using existing antibiotics.