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Characterization and Stability of Amorphous Tadalafil and Four Crystalline Polymorphs
Yuanfeng Wei1, Yunni Ling1, Meiling Su2
1School of Traditional Chinese Pharmacy, China Pharmaceutical University.
Chemical & Pharmaceutical Bulletin
|December 4, 2018
Summary
Tadalafil amorphous form (TD-AM) significantly enhances dissolution rates and maintains supersaturation, making it a promising candidate for drug development. Crystalline forms showed less favorable dissolution profiles and stability.
Area of Science:
- Pharmaceutical Sciences
- Solid-State Chemistry
Background:
- Tadalafil (TD), a phosphodiesterase-5 (PDE-5) inhibitor, suffers from poor oral bioavailability.
- Understanding the solid-state properties of Tadalafil is crucial for improving its pharmaceutical formulation.
Purpose of the Study:
- To prepare and characterize three crystalline polymorphs (TD-II, TD-III, TD-IV) and an amorphous form (TD-AM) of Tadalafil.
- To evaluate the dissolution, physical stability, and polymorphic transformation behavior of these forms.
Main Methods:
- Characterization techniques included polarized light microscopy (PLM), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), X-ray powder diffractometry (XRPD), and Fourier-transform infrared spectroscopy (FTIR).
- Dissolution testing, physical stability studies, and polymorphic transformation studies were conducted.
Main Results:
- Tadalafil amorphous form (TD-AM) exhibited a significantly higher intrinsic dissolution rate and a prolonged supersaturated state compared to crystalline forms.
- Crystalline polymorphs TD-II, TD-III, and TD-IV showed transformations to TD-I or TD-III under various conditions.
- TD-AM and crystalline TD-I demonstrated good physical stability under heating and long-term storage conditions.
Conclusions:
- The amorphous form of Tadalafil (TD-AM) presents superior dissolution properties and a prolonged supersaturated state.
- TD-AM's favorable dissolution profile and physical stability make it a highly promising candidate for further pharmaceutical product development.
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