Preparation and characterization of etoricoxib solid dispersions using lipid carriers by spray drying technique

The basic objectives of this study were to prepare and characterize solid dispersions of poorly water-soluble drug etoricoxib using lipid carriers by spray drying technique. The properties of solid dispersions were studied by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), differential scanning calorimetry (DSC), hotstage microscopy (HSM), radiograph powder diffraction (XRPD), and dissolution studies. The absence of etoricoxib peaks in XRPD profiles of solid dispersions suggests the transformation of crystalline etoricoxib into an amorphous form. In the HSM examination of solid dispersions, the dissolution of drug in the lipid carriers was observed, which was also confirmed by the absence of etoricoxib peak in DSC curves of solid dispersions. The DRIFTS spectra revealed the presence of hydrogen bonding in solid dispersions. The in vitro dissolution rate of solid dispersions as compared with pure etoricoxib, spray-dried etoricoxib, and physical mixtures of drug with lipid carriers. Therefore, the dissolution rate of poorly water-soluble drug etoricoxib can be significantly enhanced by the preparation of solid dispersions using lipid carriers by spray drying technique. Published: October 19, 2005     

Bioavailability assessment of ketoprofen incorporated in gelled self-emulsifying formulation: A technical note

Conclusion  Based on the results of the present study, it is apparent that the gelled SEF containing KPF did not significantly alter its bioavailability as compared with that of an immediate release solid dosage form when administered to human volunteers by the oral route. Published: August 10, 2005.     

Effect of system variables involved in packed column SFC of nevirapine as model analyte using response surface methodology: application to retention thermodynamics, solute transfer kinetic study and binary diffusion coefficient determination

A multifactor optimization technique is successfully applied to study the effect of simultaneously varying the system variables on feasibility of nevirapine analysis by packed column supercritical fluid chromatography (PC-SFC). The optimal conditions were determined with the aid of the response surface methodology using 3(3) factorial designs. The method is based on methanol-modified carbon dioxide as the mobile phase at flow rate of 3.0 ml/min with elution through a JASCO Finepak SIL-5, [C18 (5-micron, 25 cm x 4.6 mm, i.d.)] column using photodiode array detection. The method has been successfully used to analyze commercial solid dosage form to assess the chromatographic performance of SFC system. The present work briefs the thermodynamic applications of PC-SFC with an emphasis on the results of nevirapine. The foremost of such applications is the determination of solute diffusion coefficient in supercritical mobile phase by Taylor-Aris peak broadening technique.     

Extended Release Felodipine Self-Nanoemulsifying System

The purpose of the present study was to formulate a self-nanoemulsifying system (SNES) containing model lipophilic drug, felodipine (FLD), to improve its solubility. The SNES was formulated using varying amounts of Miglyol® 840 (as an oil), Cremophor® EL (as a surfactant), and Capmul® MCM (as a co-surfactant). The SNES were characterized for turbidity, droplet size and in vitro FLD release. The SNES containing oil, surfactant, and co-surfactant in the weight ratio of 3.5:1.0:1.0, respectively, showed good emulsification, median droplet size of 421 nm, and rapid FLD release (>90% release in 15 min). Gelling was induced in the SNES by addition of Aerosil® 200 (A 200). Rheological studies clearly demonstrated the formation of gelled microstructure with enhanced elasticity for SNES with A 200. Since FLD warrants extended delivery for management of hypertension, the gelled SNES was further encased within the hydrophobic Gelucire® 43/01 (GEL) coat to extend the release of FLD. Caprol® PGE-860 (CAP) was added to this coat as a release enhancer. No interaction was seen between GEL and CAP in differential scanning calorimetry. The effect of two formulation variables in the encased SNES, viz., the gelling agent (A200) and the release enhancer (CAP), on the in vitro FLD release was evaluated using 3² factorial design experiments. CAP by virtue of channel formation in GEL coat favored the FLD release, while the A200 retarded the FLD release by inducing gelling. At later time points, an interaction between these two variables was found to govern extended release of FLD. The developed gelled SNES encased within the GEL coat can be used as an extended release composition for lipophilic drugs.     

Development of tetracycline-serratiopeptidase-containing periodontal gel: Formulation and preliminary clinical study

The purpose of this research was to reduce the polymer concentration and to obtain reasonable viscosity at a lower concentration of pluronic by the addition of a viscosity modifier. A 20% wt/wt pluronic gel was prepared on a weight basis using the cold method. The effect of the amount of tetracycline and Aerosil on gel properties was studied. The gel was evaluated using different parameters: polarizing microscopy, gelation, gel melting, bioadhesivity, viscosity, drug release, and stability of enzyme. An in vivo study was performed to evaluate the clinical efficiency of the liquid crystalline gel. Addition of Aerosil to the gel favored hexagonal phase formation. Viscosity and bioadhesivity increased with an increase in the concentration of Aerosil. Release of tetracycline was sustained as the concentration of Aerosil increased. Various clinical parameters confirmed the acceptability and efficiency of this gel system. Published: September 15, 2006     

Flexibility between the Protease and Helicase Domains of the Dengue Virus NS3 Protein Conferred by the Linker Region and Its Functional Implications

The dengue virus (DENV) NS3 protein is essential for viral polyprotein processing and RNA replication. It contains an N-terminal serine protease region (residues 1–168) joined to an RNA helicase (residues 180–618) by an 11-amino acid linker (169–179). The structure at 3.15 Å of the soluble NS3 protein from DENV4 covalently attached to 18 residues of the NS2B cofactor region (NS2B₁₈NS3) revealed an elongated molecule with the protease domain abutting subdomains I and II of the helicase (Luo, D., Xu, T., Hunke, C., Grüber, G., Vasudevan, S. G., and Lescar, J. (2008) J. Virol. 82, 173–183). Unexpectedly, using similar crystal growth conditions, we observed an alternative conformation where the protease domain has rotated by ∼161° with respect to the helicase domain. We report this new crystal structure bound to ADP-Mn²⁺ refined to a resolution of 2.2 Å. The biological significance for interdomain flexibility conferred by the linker region was probed by either inserting a Gly residue between Glu¹⁷³ and Pro¹⁷⁴ or replacing Pro¹⁷⁴ with a Gly residue. Both mutations resulted in significantly lower ATPase and helicase activities. We next increased flexibility in the linker by introducing a Pro¹⁷⁶ to Gly mutation in a DENV2 replicon system. A 70% reduction in luciferase reporter signal and a similar reduction in the level of viral RNA synthesis were observed. Our results indicate that the linker region has evolved to an optimum length to confer flexibility to the NS3 protein that is required both for polyprotein processing and RNA replication.     

Novel pyrrolidine heterocycles as CCR1 antagonists

A novel series of pyrrolidine heterocycles was prepared and found to show potent inhibitory activity of CCR1 binding and CCL3 mediated chemotaxis of a CCR1-expressing cell line. A potent, optimized triazole lead from this series was found to have acceptable pharmacokinetics and microsomal stability in rat and is suitable for further optimization and development.     

Reduced Ulcerogenic Potential and Antiarthritic Effect of Chitosan–Naproxen Sodium Complexes

The purpose of this research was to address the utility of naproxen sodium–chitosan spray-dried complexes for antiulcer and antiarthritic activities. The cold stress technique was used to examine the ulcerogenic potential of naproxen sodium (NPX) and spray-dried formulations in the different doses. The ulcerations reduced with the dose of spray-dried complexes of naproxen sodium and chitosan. The conspicuous hemorrhagic lesions were visible in the morphological features of the animal treated with naproxen 50 mg/kg (p.o.). Thus, the results suggest that the spray-dried naproxen sodium–chitosan complex (NPXF) was not corrosive to the gastric mucosa at high doses of 50, 100, and 200 mg/kg (p.o.) under stressful conditions. It is evident from the present investigation that NPXF does not possess any ulcerogenic potential in comparison to naproxen which, under stressful conditions, led to the hypersecretion of HCl, culminating to petichial hemorrhages in the gastric mucosa of the animals. The biphasic pattern was observed in the various arthritic parameters. The rise in paw volume, joint diameter, WBC count, arthritis score, and fall in body weight was significantly ameliorated in the animals treated with NPXF (5, 10, and 20 mg/kg, p.o). At the end of the study, slight erythema was visible in the naproxen-treated animals. However, no erythema, redness, or ulcers were visible in the animals treated with NPXF. Thus, the direct compression properties and reduced ulcerogenic activity, combined with the demonstrated solubilizing power and analgesic effect enhancer ability toward the drug, make naproxen sodium–chitosan spray-dried complexes particularly suitable for developing a reduced-dose, fast-release, solid oral dosage form of naproxen.Key words: antiarthritic, chitosan complexes, ulcer     

2-Benzimidazolyl-9-(chroman-4-yl)-purinone derivatives as JAK3 inhibitors

A novel class of Janus tyrosine kinase 3 (JAK3) inhibitors based on a 2-benzimidazoylpurinone core structure is described. Through substitution of the benzimidazoyl moiety and optimization of the N-9 substituent of the purinone, compound 24 was identified incorporating a chroman-based functional group. Compound 24 shows excellent kinase activity, good oral bioavailability and demonstrates efficacy in an acute mechanistic mouse model through inhibition of interleukin-2 (IL-2) induced interferon-γ (INF-γ) production.     

Effect of Drying Methods on Swelling,Erosion and Drug Release from Chitosan–Naproxen Sodium Complexes

The purpose of this research was to explore theapplication of ionic interactions between naproxen sodium (NS) and chitosan (CH) in complexes (NSC) prepared by tray drying (TD) and spray drying (SD) methods. Drug–polymer ratio (1:1) in the NSC was optimized on the basis of dialysis studies. The particulate systems of NSC were prepared by tray drying (TD) and spray drying (SD) methods. Release retarding polymers were added to the NSC and to the physical mixtures containing NS–CH and their effects on water uptake, matrix erosion and drug release at different pH were compared. Spray dried complexes (SDC) were spherical, free flowing, light and fine amorphous particles in contrast to the crystalline, hard, tenacious, irregularly shaped, denser tray dried complexes (TDC) with poor flowability. Differential scanning calorimetry (DSC), powder X-ray diffraction (PXRD) and Fourier transform infrared (FTIR) patterns confirm the conversion of crystalline to high energy amorphous phase suitable for ionic interactions in NSC. Presence of release retarding polymers, kappa carrageenan and hydroxypropylmethylcellulose (HPMC) in the NSC compacts retarded the drug release and improved the matrix integrity. Carrageenan matrices exhibited more retardation than HPMC tablets. FTIR patterns, erosion, swelling and drug release from matrices support ionic interactions between NS and CH in NSC. The reasons for retarded drug release from the chitosan matrices at acidic pH include poor solubility of drug at acidic pH, formation of a rate limiting polymer gel barrier along the periphery of matrices and the ionic interactions between oppositely charged moieties.