Anti-oxidant Containing Nanostructured Lipid Carriers of Ritonavir: Development, Optimization, and In Vitro and In Vivo Evaluations.

Acquired immunodeficiency syndrome (AIDS) is a condition caused by the infection of a retrovirus namely, human immunodeficiency virus (HIV). Currently, highly active anti-retroviral therapy (HAART), a combination of anti-viral drugs belonging to different classes is considered to be effective in the management of HIV. Ritonavir, a protease inhibitor (PI), is one of the most important components of the HAART regimen. Because of its lower bioavailability and severe side effects, presently, ritonavir is not being used as a PI. However, this drug is being used as a pharmacokinetic boosting agent for other PIs such as lopinavir and in lower doses. The current study aimed to develop nanostructured lipid carriers (NLCs) encapsulating ritonavir to reduce its side effects and enhance oral bioavailability. Ritonavir-loaded NLCs were developed using a combination of two different solid lipids and liquid lipids. Alpha-tocopherol, a well-known anti-oxidant, was used as an excipient (liquid lipid) in the development of NLCs which were prepared using a simple hot-emulsion and ultrasonication method. Drug-excipient studies were performed using Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). QbD approach was followed for the screening and optimization of different variables. The developed NLCs were characterized for their particle size (PS), polydispersity index (PDI), zeta potential (ZP), and entrapment efficiency (EE). Furthermore, NLCs were studied for their in vitro drug release profile, and finally, pharmacokinetic parameters were determined using in vivo pharmacokinetic studies. The optimized NLC size was in the range of 273.9 to 458.7 nm, PDI of 0.314 to 0.480, ZP of -52.2 to - 40.9 mV, and EE in the range of 47.37 to 74.51%. From in vitro drug release, it was found that the release of drug in acidic medium was higher than phosphate buffer pH 6.8. Finally, in vivo pharmacokinetic studies revealed a 7-fold enhancement in the area under the curve (AUC) and more than 10-fold higher Cmax with the optimized formulation in comparison to pure drug suspension. Graphical Abstract.