Formulation and characterization of solid lipid nanoparticles for an anti-retroviral drug darunavir

Darunavir, an anti-HIV drug having poor solubility in aqueous and lipid medium, illustrates degradation above its melting point, i. e. 74 degrees C, thus, posing a challenge to dosage formulation. Despite, the drug suffers from poor oral bioavailability (37%) owing to less permeability and being poly-glycoprotein and cyp3A metabolism substrate. The study aimed formulating a SLN system to overcome the formulation and bioavailability associated problems of the drug. Based on the drug solubility and stable dispersion findings, lipid and surfactant were chosen and nanoparticles were prepared using hot-homogenization technique. Optimization of variables such as lipid concentration, oilsurfactant and homogenization cycle was carried and their effect on particle size and entrapment efficiency was studied. Freeze-dried SLN further characterized using SEM, DSC and PXRD analysis revealed complete entrapment of the drug and amorphous nature of the SLN. In vitro pH release studies in 0.1 N HCl and 6.8 pH buffer demonstrated 84 and 80% release at the end of 12th h. The apparent permeability of the SLN across rat intestine was found to be 24 x 10(-6) at 37 degrees C at the end of 30 min while at 4 degrees C the same was found to be 5.6 x 10(-6) prompting involvement of endocytic processes in the uptake of SLN. Accelerated stability studies revealed no prominent changes upon storage.