Rahul Vats

Lipid nanoparticles for oral delivery of raloxifene: Optimization, stability, in vivo evaluation and uptake mechanism

Raloxifene HCl (RLX) shows low oral bioavailability (<2%) in humans due to poor aqueous solubility and extensive (>90%) metabolism in gut. Lipid nanoparticles (SLN) with glyceryl tribehenate were designed to enhance drugs oral bioavailability. Box-Bhenken design was used to optimize manufacturing conditions. Optimized SLN had particle size of 167±3nm and high encapsulation efficiency (>92%). Oral bioavailability of RLX from SLN was improved by 3.24 folds compared to free RLX in female Wistar rats. Both clathrin and caveolae mediated endocytosis pathways were involved in the uptake of SLN. Lymphatic transport inhibitor, cycloheximide significantly reduced oral bioavailability of SLN.

A hybrid design to optimize preparation of lopinavir loaded solid lipid nanoparticles and comparative pharmacokinetic evaluation with marketed lopinavir/ritonavir coformulation.

To prepare stearic acid‐based lopinavir (LPV) loaded solid lipid nanoparticles (SLNs) using a hybrid design and compare in‐vivo performance of optimized formulation with marketed LPV/ritonavir (RTV) coformulation.

Design, optimization and evaluation of poly-ɛ-caprolactone (PCL) based polymeric nanoparticles for oral delivery of lopinavir

Abstract Lopinavir (LPV)-loaded poly-ε-caprolactone (PCL) nanoparticles (NPs) were prepared by emulsion solvent evaporation technique. Effects of various critical factors in preparation of loaded NPs were investigated. Box–Behnken design (BBD) was employed to optimize particle size and entrapment efficiency (EE) of loaded NPs. Optimized LPV NPs exhibited nanometeric size (195.3 nm) with high EE (93.9%). In vitro drug release study showed bi-phasic sustained release behavior of LPV from NPs. Pharmacokinetic study results in male Wistar rats indicated an increase in oral bioavailability of LPV by 4-folds after incorporation into PCL NPs. From tissue distribution studies, significant accumulation of loaded NPs in tissues like liver and spleen indicated possible involvement of lymphatic route in absorption of NPs. Mechanistic studies using rat everted gut sac model revealed endocytosis as a principal mechanism of NPs uptake. In vitro rat microsomal metabolism studies demonstrated noticeable advantage of LPV NPs by affording metabolic protection to LPV. These studies indicate usefulness of PCL NPs in enhancing oral bioavailability and improving pharmacokinetic profile of LPV.

Modified pullulan nanoparticles for oral delivery of lopinavir: formulation and pharmacokinetic evaluation.

In this investigation, we report the use of the pullulan acetate, a hydrophobic derivative of pullulan in the formulation of Lopinavir loaded nanoparticles meant for oral delivery. Pullulan was modified to pullulan acetate by acetylation process in the presence of pyridine; acetylation was confirmed by FT-IR and NMR spectra. Lopinavir, an HIV-protease inhibitor was formulated into nanoparticles of pullulan acetate by the well-known emulsion-solvent-evaporation method. The nanoparticles were tested for particle size, entrapment efficiency, in-vitro drug release and stability. Further, extensive pharmacokinetic and tissue distribution studies were performed in Wistar rats. The results showed that, with our method, we could obtain nanoparticles of ∼197 nm, high entrapment efficiency (∼75%) and monodisperse nature (PDI<0.2). Stability data showed that the nanoparticles were stable over a period of 3 months. From the pharmacokinetic study data, we found that the relative bioavailability of Lopinavir from nanoparticles was ∼2 folds higher than the free drug. Moreover, the tissue distribution study showed a higher distribution of Lopinavir loaded nanoparticles to lymphoid organs (liver, spleen and lymph nodes that are also important viral reservoirs in HIV infection). Thus, we conclude that Lopinavir loaded nanoparticle could be a superior alternative approach to free Lopinavir in treating HIV infection.

Effect of Grapefruit Juice and Ritonavir on Pharmacokinetics of Lopinavir in Wistar Rats

Lopinavir (LPV), a newer HIV protease inhibitor, has poor bioavailability being a substrate of both cytochrome P450 3A enzyme system (CYP3A) and permeability‐glycoprotein (P‐gp). Ritonavir (RTV) is a known inhibitor of both P‐gp and CYP3A and is co‐administered with LPV in anti‐HIV therapy. Grapefruit juice (GFJ) is known to inhibit CYP3A and has conflicting effects, ranging from activation to inhibition, on P‐gp. In this research work, the effects of GFJ and RTV on the pharmacokinetics of LPV were compared in rats. A mechanistic evaluation was undertaken using various in vitro and ex vivo studies to support the in vivo pharmacokinetic data. The plasma levels of LPV were found to increase significantly upon co‐administration with GFJ in single dose as well as multidose pretreatment studies. Similar, but marginally higher, results were observed upon co‐administration of LPV with RTV. No significant change in tmax was observed in the various treatment groups. The apparent permeability of LPV in the ileum increased significantly after the pre‐incubation with GFJ and RTV compared with no pre‐incubation. The GFJ and RTV showed a significant and similar inhibitory effect on rat intestinal microsomes in the metabolism of LPV. The GFJ was equally effective as RTV in increasing the bioavailability of LPV. Copyright

Engineering another class of anti-tubercular lead: Hit to lead optimization of an intriguing class of gyrase ATPase inhibitors.

A structure based medium throughput virtual screening campaign of BITS-Pilani in house chemical library to identify novel binders of Mycobacterium tuberculosis gyrase ATPase domain led to the discovery of a quinoline scaffold. Further medicinal chemistry explorations on the right hand core of the early hit, engendered a potent lead demonstrating superior efficacy both in the enzyme and whole cell screening assay. The binding affinity shown at the enzyme level was further corroborated by biophysical characterization techniques. Early pharmacokinetic evaluation of the optimized analogue was encouraging and provides interesting potential for further optimization.

Simple, Rapid and Validated LC Determination of Lopinavir in Rat Plasma and its Application in Pharmacokinetic Studies.

Lopinavir is a new specific and potent HIV-1 protease inhibitor. A simple and rapid Reverse Phase High-Performance Liquid Chromatographic method using UV detection was developed and validated for the analysis of lopinavir in rat plasma under isocratic conditions. The method involves a single step protein precipitation technique. The detector response was linear over the concentration range of 250 to 4000 ng mL −1. High recovery ranging from 97.5 to 101.2 percent was obtained which precludes the use of internal standard. The developed method was validated as per standard guidelines. Validation of the developed method demonstrated accuracy, precision and selectivity of the proposed method. The drug was found to be stable under various processing and storage conditions. This rapid and cost-effective method was successfully applied in the estimation of lopinavir and determination of various pharmacokinetic parameters during post intravenous bolus administration of the drug in rats. The developed method can be suitably employed in preclinical pharmacokinetic evaluation of new formulations designed to improve the bioavailability of lopinavir.

Poly (ε-caprolactone) nanocapsules for oral delivery of raloxifene: process optimization by hybrid design approach, in vitro and in vivo evaluation

Abstract Raloxifene HCl (RLX), a selective oestrogen receptor modulator, has low oral bioavailability (<2%) in humans due to its poor aqueous solubility and extensive first-pass metabolism in gut. In this study, we optimised the method of preparation for poly (ε-caprolactone) (PCL) based nanocapsules of RLX by double emulsion method (w/o/w). A hybrid design approach, Plackett–Burman design followed by rotatable central composite design, was used to arrive at the optimised formulation. The optimised formulation was subjected to in vitro and in vivo evaluation. RLX loaded nanocapsules were spherical in shape with particle size less than 200 nm and high encapsulation efficiency (>80%). RLX-loaded nanocapsules showed 2.1-fold increase in oral bioavailability compared to free RLX. IV pharmacokinetic studies indicated that RLX loaded into nanocapsule had significantly low clearance in comparison with free RLX. Designed nanocapsules showed promise as delivery systems to enhance oral bioavailability and in reducing clearance of raloxifene.

Validation of a Simple, Rapid and Sensitive LC Method for Quantification of Riluzole in Rat Plasma and its Pharmacokinetic Application

Abstract A simple, sensitive and rapid high-performance liquid chromatography method with ultraviolet (UV) detector was developed and validated for the analysis of riluzole (RLZ) in rat plasma. The plasma sample, spiked with nebivolol as an internal standard (IS), was subjected to a single step protein precipitation prior to analysis. Chromatographic separation was achieved on a Phenomenex C18 (250 mm× 4.6 mm, 5 µm) column. A combination of methanol and phosphate buffer (25 mM KH 2 PO 4 , pH 3.5), in the ratio of 70:30% v/v was used as the mobile phase in isocratic mode. RLZ and IS were monitored at wavelengths of 264 nm and 280 nm respectively. No interference was observed from plasma components in the analysis of RLZ and IS. The calibration curve was linear over the range of 50–4000 ng/mL (r 2 = 0.999). The drug was found to be stable under various processing and storage conditions. The assay provided good reproducibility, accuracy and proved to be suitable for oral pharmacokinetic studies of RLZ in rats.

Drug–drug interaction study to assess the effects of atorvastatin co‐administration on pharmacokinetics and anti‐thrombotic properties of cilostazol in male Wistar rats

Cilostazol (CLZ) and atorvastatin (ATV) are often co‐prescribed to treat conditions such as peripheral arterial disease. In the present study, the drug–drug interaction potential of multi‐dose ATV co‐administration with CLZ on both pharmacokinetics and the anti‐thrombotic property of CLZ is demonstrated. The pharmacokinetic parameters of CLZ (6 mg/kg, twice daily) were determined in male Wistar rats after 7 days co‐administration with ATV (5 mg/kg, once daily) in order to assess the interaction potential between CLZ and ATV on chronic treatment. In vitro metabolic inhibition and everted gut sac studies were conducted to elucidate the mechanism of this interaction. Pharmacodynamic drug–drug interaction was evaluated on anti‐thrombotic models including time to occlusion, platelet aggregation and rat tail bleeding time. A validated LC‐MS/MS method was employed simultaneously to quantify both ATV and CLZ in rat plasma matrix. A statistically significant increase in systemic exposure (Cssmax by ~1.75 fold; AUC by ~3.0 fold) to CLZ was observed in ATV pre‐treated rats. In vitro metabolism studies using liver microsomes (RLM and HLM) demonstrated statistically significant inhibition of CLZ metabolism when co‐incubated with ATV. No change in apparent permeability of CLZ was observed in the presence of ATV. Atorvastatin showed a significant delay in artery occlusion time without altering CLZs bleeding time and platelet aggregation profile. Collectively the results of these studies provide metabolic insight into the nature of drug–drug interaction between the selected drugs. Co‐administration with ATV influences the pharmacokinetics and anti‐thrombotic property of CLZ. A thorough clinical investigation is required before extrapolation of data to humans. Copyright