Punna Rao Ravi

Design and study of lamivudine oral controlled release tablets

The objective of this study was to design oral controlled release matrix tablets of lamivudine using hydroxypropyl methylcellulose (HPMC) as the retardant polymer and to study the effect of various formulation factors such as polymer proportion, polymer viscosity, and compression force on the in vitro release of drug. In vitro release studies were performed using US Pharmacopeia type 1 apparatus (basket method) in 900 mL of pH 6.8 phosphate buffer at 100 rpm. The release kinetics were analyzed using the zero-order model equation, Higuchi’s square-root equation, and the Ritger-Peppas empirical equation. Compatibility of the drug with various excipients was studied. In vitro release studies revealed that the release rate decreased with increase in polymer proportion and viscosity grade. Increase in compression force was found to decrease the rate of drug release. Matrix tablets containing 60% HPMC 4000 cps were found to show good initial release (26% in first hour) and extended the release up to 16 hours. Matrix tablets containing 80% HPMC 4000 cps and 60% HPMC 15 000 cps showed a first-hour release of 22% but extended the release up to 20 hours. Methematical analysis of the release kinetics indicated that the nature of drug release from the matrix tablets was dependent on drug diffusion and polymer relaxation and therefore followed non-Fickian or anomalous release. No incompatibility was observed between the drug and excipients used in the formulation of matrix tablets. The developed controlled release matrix tablets of lamivudine, with good initial release (20%–25% in first hour) and extension of release up to 16 to 20 hours, can overcome the disadvantages of conventional tablets of lamivudine.

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.

Nasal in-situ gels for delivery of rasagiline mesylate: improvement in bioavailability and brain localization

Abstract Intranasal thermosensitive gel for rasagiline mesylate (RM) was developed for effective treatment of Parkinson’s disease. Intranasal gels were prepared by combination of poloxamer 407 and poloxamer 188 (1:1) with mucoadhesive polymers (carbopol 934 P and chitosan). The formulations were evaluated for sol–gel transition temperature, in-vitro drug release and in-vivo mucociliary transit time. Further, optimal intranasal gel formulations were tested for in-vivo pharmacokinetic behavior, nasal toxicity studies and brain uptake studies. It was found that optimal formulations had acceptable gelation temperature (28–33 °C) and adequate in-vitro drug release profile. Pharmacokinetic study in rabbits showed significant (p < 0.05) improvement in bioavailability (four- to six-folds) of the drug from intranasal gels than oral solution. Chronic exposure studies in Wistar rats showed that these intranasal gels were non-irritant and non-toxic to rat nasal mucosa. Estimation of RM in rat brain tissue showed significant (p < 0.01) improvement in uptake of RM form intranasal gel formulations than nasal solution.

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.

LC Method for Determination of Rasagiline Mesylate in Different Plasma Matrices and its Application to Oral Pharmacokinetic Study in Rabbits

A simple, rapid and sensitive reverse-phase liquid chromatographic method is developed and validated for estimation of rasagiline mesylate in different plasma matrices (rat, rabbit and human plasma). The method employs an isocratic elution technique with a Kromasil C18 column and has an optimized mobile phase composition of 10 mM ammonium acetate buffer-acetonitrile (40:60 v/v). The plasma samples displayed linear detector responses in the concentration range of 0.5-20 µg/mL in all plasma matrices when monitored at 265 nm using an ultraviolet detector. Because the simple protein precipitation method yields over 95% recovery of rasagiline mesylate from all plasma matrices, no internal standard was used in this method. A detailed validation study of the method proves the accuracy, precision and selectivity (in estimating rasagiline mesylate) in all plasma matrices. The drug is also stable under various processing and storage conditions in all plasma matrices, as evident from the study. The present method was applied to determine the drug-protein binding ratio in all the plasma matrices. The use of this method in determining pharmacokinetic parameters of rasagiline mesylate by non-compartmental analysis after oral dosing in rabbits is also discussed.

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

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.