Purpose: Despite several advances in healthcare, treatment of Acquired Immunodeficiency Syndrome (AIDS) remains a major health challenge. The formulation of anti-retroviral therapy (ART) for the pediatric and geriatric population poses a major challenge owing to reasons like their age, weight and other parameters that change their growth. Also, the increasing cost and poor access to medications, and unpalatability is a major obstacle to the adherence of ART. The therapeutic management of AIDS includes a combination of three or more antiretroviral drugs from more than one class or same class which helps to prevent drug resistance. Of late, Ritonavir (RTV) and Darunavir (DRV) combination have been recommended as 2nd line anti-HIV drugs, according to WHO dosing guidance. Nevertheless, both these drugs suffer from poor oral bioavailability leading to an increase in its dose. In the present study, an attempt has been made to boost the oral bioavailability of DRV by co-administration with ritonavir RTV using combinative method i.e. high shear homogenization (HSH) followed by the probe sonication method by formulating it into fixed-dose combination nanosuspension (FDC-NS). In addition, computational tools were used to select suitable solvents for the preparation of nanosuspension and to understand the mechanism of nanoparticle formation in the nanosuspension which reduces the time and cost involved in experimental approaches.
Methods: The solvent selection was carried out by solubility parameter and solvation energy using computation tools like Schrödinger Materials Science Suite (MSS). Based on the preliminary results obtained, the Fractional Factorial design was used for the screening and optimization of material and process parameters. The formulation batches were characterized and evaluated for their particle size, zeta potential, saturation solubility, in vitro drug release and in vivo pharmacokinetics. Solid state characterization was done by using Fourier-transform infrared spectroscopy (FTIR), Differential Scanning Calorimetry (DSC) and X-Ray Diffraction (XRD). The mechanism of nanoparticle formation in nanosuspension was studied and analyzed by utilizing computational tools using Schrödinger Materials Science Suite (MSS).
Results: Based on computational studies, a combination of acetone and acetonitrile was selected as suitable solvents for the nanosuspension preparation. The particle size, PDI and zeta potential of the final optimized formulation was found to be 389.45 ± 4.59 nm, 0.431 ± 0.009 and -26.825 ± 0.17 mV, respectively. The drug content of Darunavir and Ritonavir was 88.5 ± 2.5 and 78.67 ± 3.42 % respectively. The release study indicated improved dissolution profile of nanosuspension compared to a pure drug suspension. Solid state characterization by FTIR, DSC and XRD indicated decreased crystallinity of drugs in the nanoform. The visual observation in addition to analyzed parameters like diffusion coefficient calculation, radial distribution function, hydrogen bond determination, the radius of gyration calculation and density profile confirmed the formation of drug core upon addition of the anti-solvent and the polymer stabilizer capping the drug molecules core. Further, the removal of the solvent resulted in the formation of the stable particle with core confined to DRV and RTV, which were capped by the polymer poloxamer 407. The in vivo pharmacokinetic studies revealed an increase in Cmax and AUC for both DRV and RTV in case of FDC-NS. DRV showed 0.6 ± 0.01 µg/ml Cmax when administered in fasting state. The Cmax (3.4±0.5 µg/ml for DRV, 11.4±1.3 µg/ml for DRV+RTV nanosuspension) and AUC (44.4±6.4 g-h/ml for DRV, 149.8±15.2 g-h/ml for DRV+RTV nanosuspension) of DRV were significantly increased on coadministration with RTV in nanosuspension form. When administered with food the Cmax and AUC were relatively higher compared to fasting state. There was no significant change in the pharmacokinetic profile of RTV. However significant change was observed in plasma concentration of RTV in the form of nanosuspension formulation. In fed state 3 fold increase in Cmax (0.5±0.1 to 1.4±0.3 µg/ml) was observed. However, only two fold increase was observed in fasting state. Similar effects were observed with AUC.
Conclusion: The study demonstrates successful formulation development of DRV/RTC FDC nanosuspension with improved bioavailability. Combination of experimental and computational approaches plays a crucial role in the drug design and development by saving time and cost. The developed formulation may be a suitable alternative to the current Anti-HIV therapy for both the pediatrics and the geriatrics.
Chetan Mehta– Manipal College of Pharmaceutical Sciences