Tadalafil oral disintegrating tablets: an approach to enhance tadalafil dissolution

Improvement of the dissolution behavior of poorly water soluble tadalafil using solid dispersion technique was investigated. Polyvinylpyrollidone (PVP) was used to prepare solid dispersions (SDs) based on different ratios; 1:1 (SD 1 ,), 1:2 (SD 2 ,), 1:3 (SD 3 ), 1:4 (SD 4 ,) respectively. Tadalafil/PVP/Avicel ® in a ratio of 1:2:2 respectively (SD 5 ) was also prepared. SD5 was selected to formulate orally disintegrating tablets (ODTs). Five formulae were prepared (F 1 –F 5 ) and characterized with respect to drug content uniformity, breaking strength, % friability, wetting behavior, oral disintegration time. Results revealed that SD 2 exhibited the highest dissolution rate improvement, where mean dissolution time was 8.22 min compared to 60.12 min for free tadalafil. X-ray powder diffraction spectroscopy and differential scanning calorimetry showed partial drug amorphization in the tested SDs sample which was further confirmed by scanning electron microscope. Moreover, particle size analysis showed the presence of nanocrystals combined with microcrystals dispersed in the prepared SDs. Among the studied solid SDs, SD 2 showed the most satisfactory results. In order to improve % yield of SD 2 (70.14 %), avicel ® was added and the resulting tertiary combination (SD 5 ) showed better flow and higher % yield value (94.22 %). % tadalfil released from SD 2 & SD 5 differ insignificantly (p ≥ 0.05). F 3 (48 % mannitol, 16 % avicel ® , 16 % croscarmellose) showed superior wetting time (30.1 s), excellent oral disintegration time (20 s) with an accepted hardness (3.6 kg) & % friability (0.7). Additionally, F 3 exhibited a significant improvement of tadalafil dissolution compared to that of pure drug and test commercial tablet brand (p ≤ 0.05).