Formulation with Povacoat® to Prevent Aggregation of Rifampin Nanocrystal Using High-Pressure Homogenization

Purpose The rifampin, a class II drug according to the Biopharmaceutics Classification System (BCS), is the first-line treatment for tuberculosis (TB). This poorly water-soluble drug presents variable bioavailability and develops resistance quickly during the treatment. As a result, tuberculosis is still a challenging problem for public health at a global level. Povacoat ®, a hydrophilic PVA copolymer, has been using as a dispersion stabilizer to overcome aggregation of low water solubility drugs in the development of drug nanocrystals. Among the techniques to obtain nanocrystals, the high-pressure homogenization has a high reproducibility, it is easy to handle and can be applied at a large-scale plant at relatively low cost. Methods The nanosuspension of rifampin was prepared using high-pressure homogenization using Nano DeBEE® (piston-gap homogenizer). The formulation containing 2.5% (w/w) rifampin and 10% (w/w) Povacoat®, as stabilizer, was pre-milling with an ultra turrax T25 for 5 min at 24000 rpm, followed by 3 pre-milling homogenization cycles at 500 bar and 5 cycles at 1000 bar. High-pressure homogenization at 1500 bar was applied for 15 homogenization cycles to obtain the nanosuspension. The micronized rifampin was evaluated using laser diffraction (LD) while rifampin nanosuspension by LD and Dynamic Light Scattering (DLS) as methods to determine the particles size. Zeta potential was measured using laser doppler electrophoresis and the polydispersity index (PI) was measured to determine the width of the size distribution.The morphology and size were observed using scanning electron microscope (MEV) for micronized rifampin and transmission electron microscope (TEM) for the formulation. The results of microscopes were evaluated using Image.j program. The stability of rifampin nanosuspension was investigated with the aim to determine the effect of the Povacoat® on the physical stability of the preparation. A short-term stability test was performed at different temperatures (room temperature (RT) and 4&[deg]C) for 120 days. HDM, PI and zeta potential were evaluated as a function of time. Results The rifampin nanocrystals using Povacoat® as stabilizer were successfully prepared by high-pressure homogenization. The particles size distribution of the micronized rifampin by LD was D10: 35.17 ± 0.04 µm ; D50: 48.86 ± 0.03 µm and D90: 66.77± 0.04 µm with z- average: 50.08 ± 0.03 µm and for rifampin nanosuspension was D10: 0.07± 0.01 µm ; D50: 0.32 ± 0.01 µm and D90: 0.97± 0.02 µm with z- average equal to 0.44 ± 0.01 µm. The dynamic light scattering (DLS) revealed hydrodynamic mean diameter (HDM) of 412. 60 ± 4.1 nm with PI of 0.12 ± 0.02 and zeta potential of -9.94 ± 0.19 mV. The MEV of the micronized rifampin showed crystal structure and average size of 71.04 ± 10.14 µm. The rifampin nanocrystals observed by TEM presented semi-spherical morphology with average size of 256. 15 ± 28.29 nm. The rifampin nanocrystals were approximately 110-fold smaller than the micronized drug. The stability of the formulation is stable over the period of 120 days at both storage conditions. Conclusion The rifampicin nanocrystals showed suitable physical-chemical characteristics and support the use the Povacoat® as stabilizer to avoid aggregation. The rifampin nanosuspensions presented a good stability as a function of time.