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- Discovery of anti-virulence agents against MRSA. [JOURNAL ARTICLE]
- Antimicrob Agents Chemother 2013 May 20.
Anti-virulence agents inhibit the production of disease-causing virulence factors but are neither bacteriostatic nor bactericidal. Anti-virulence agents against MRSA strain USA300, the most widespread community-associated MRSA strain in the US, were discovered by virtual screening against the response regulator AgrA, which acts as a transcription factor for the expression of several of the most prominent S. aureus toxins and virulence factors involved in pathogenesis. Virtual screening was followed by similarity searches in databases of commercial vendors. These small-molecule compounds inhibit the production of the toxins α-hemolysin and phenol-soluble modulin-α in a dose-dependent manner without inhibiting bacterial growth. These anti-virulence agents are small-molecule biaryl compounds in which the aromatic rings are either fused or separated by a short linker. One of these compounds is the FDA-approved non-steroidal anti-inflammatory drug diflunisal. This represents a new use for an old drug. Anti-virulence agents might be useful in prophylaxis and as adjuvants in antibiotic therapy of MRSA infections.
- Solubility enhancement of Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) using polypolypropylene oxide core PAMAM dendrimers. [JOURNAL ARTICLE]
- Int J Pharm 2013 Apr 28; 451(1-2):18-22.
The aim of the present study was to evaluate the aqueous solubility enhancement properties of polypropylene oxide cored PAMAM (PPO@PAMAM) dendrimers. The solubility of NSAIDs (Ketoprofen, Ibuprofen and Diflunisal) was investigated in the presence of PPO@PAMAM dendrimers at room temperature in buffer solution. The effects of dendrimer concentration, generation and core size on the solubility of NSAIDs have been investigated. The experimental results showed that the solubility of the NSAIDs was approximately proportional to dendrimer concentration and generation. In addition, the effect of core size on the solubility of NSAIDs in constant generation and concentration of PPO@PAMAM dendrimer was Ketoprofen>Diflunisal>Ibuprofen. Under optimized conditions, PPO@PAMAM dendrimers are highly effective solubility enhancer for NSAIDs due to its new polypropylene oxide core.
- A new hydrate form of diflunisal precipitated from a microemulsion system. [JOURNAL ARTICLE]
- Colloids Surf B Biointerfaces 2013 Apr 6.:68-73.
Three microemulsion systems were applied as solvents for polymorph screening of seven active pharmaceutical ingredients (APIs): carbamazepine, piroxicam, sulfaguanidine, nitrofurantoin, theophylline, quercetin, and diflunisal. All the recrystallized compounds were examined by using powder X-ray diffractometry, differential scanning calorimetry, elemental analysis, Karl Fischer titration and dissolution rate. A new crystal form of diflunisal hydrate was discovered by the cooling method of recrystallization in a water-in-oil microemulsion system, composed of water, alkane and dioctyl sodium sulfosuccinate. The new hydrate form of diflunisal was characterized and confirmed to be a stoichiometry of diflunisal:water of 1:1. The other two microemulsion systems were able to convert the anhydrous diflunisal Form I to Form III. The dissolution rate of diflunisal hydrate is unexpectedly much higher than that of anhydrous ones (Forms I and III). All the other six APIs (carbamazepine, piroxicam, sulfaguanidine, nitrofurantoin, theophylline and quercetin) recrystallized from the microemulsion systems were all converted into hydrate form.
- Comparative in vitro dissolution and in vivo bioavailability of diflunisal/naproxen fixed-dose combination tablets and concomitant administration of diflunisal and naproxen in healthy adult subjects. [Journal Article]
- Drug Res (Stuttg) 2013 Mar; 63(3):150-8.
A simple validated high-performance liquid chromatography (HPLC) assay was developed for determination of diflunisal and naproxen in human plasma samples. This is to compare the bioavailability of diflunisal-naproxen fixed-dose combination (FDC) with their separate dosage forms. The in vitro dissolution study was adopted to compare the dissolution behavior of FDC with respect to separate marketed tablets. In vivo study was conducted according to a single-center, randomized, single-dose, laboratory-blinded, 2 Way, Cross-Over Study with a washout period of 10 days. Under fasting conditions, 24 healthy Egyptian male volunteers were randomly allocated to receive a single oral dose of either one FDC tablet or co-administration of two separate diflunisal and naproxen marketed tablets. Plasma samples were obtained over a 72-h interval and analyzed for diflunisal and naproxen by reversed phase liquid chromatography with UV detection. The pharmacokinetic parameters Cmax, AUC0-t, AUC0-∞, tmax, and t1/2 were determined from plasma concentration-time profiles. The 90% confidence intervals for the ratio of log transformed values of Cmax, AUC0-t, and AUCt-∞ of the 2 treatments were within the acceptable range (0.8-1.25) for bioequivalence. From pharmacokinetic and in vitro studies perspectives, 1 FDC tablet demonstrated similar relative bioavailability with the 2 individual -reference tablets.
- Human serum albumin-based design of a diflunisal prodrug. [JOURNAL ARTICLE]
- Eur J Pharm Biopharm 2013 Feb 14.
The cyclooxygenase-2 inhibitor, diflunisal, is used in the clinic for its anti-inflammatory activity. About 99% of a dose of diflunisal is unavailable for reaction with the target enzyme, because diflunisal strongly binds to human serum albumin (HSA). To reduce the binding affinity of diflunisal to albumin, we designed and synthesized the prodrug acetyldiflunisal. The crystal structure of HSA complexed with fatty acid and acetyldiflunisal revealed that acetyldiflunisal binds to the IIA subdomain and that upon binding, it acetylates lysine 199. Mass spectrometry confirmed that acetyldiflunisal acetylates Lys199. The acetylated albumin had twofold weaker binding affinity for diflunisal as demonstrated by fluorescence quenching. Reduced binding affinity means that diflunisal is more easily released from acetylated albumin into the circulation. Therefore, lower doses of acetyldiflunisal compared to diflunisal will be required. Taken together, our results not only provide a template for design of HSA-based prodrugs, but also pave the way toward more effective use of diflunisal in the clinic.
- Cyclodextrin-crosslinked poly(acrylic acid): Synthesis, physicochemical characterization and controlled release of diflunisal and fluconazole from hydrogels. [Journal Article, Research Support, Non-U.S. Gov't]
- Int J Pharm 2013 Feb 28; 444(1-2):175-84.
The aim of this work was to develop mucoadhesive hydrogels with variable drug delivery properties by crosslinking poly(acrylic acid) (PAA) with cyclodextrins (CDs). CD-PAA polymers with high CD content and good inter-batch reproducibility were synthesized by activating PAA with SOCl2, then reacting PAA chloride with CD in the presence of 4-dimethylaminopyridine at 50°C. Manipulation of the synthesis conditions affected the physicochemical character of the CD-PAA polymers and hydrogels in terms of CD content, the average number of ester bonds to an individual CD, viscosity, and the association and release of model drugs. Inclusion complexation of diflunisal (DIF) and fluconazole (FLZ) with CD-PAA hydrogels was assessed by (19)F NMR spectroscopy and association constants (Kas) for DIF were in the range 220-486M(-1) with βCD-PAA and 1327-6055M(-1) with hydroxypropyl-βCD-PAA. For FLZ the Ka range was 34-171M(-1) with hydroxypropyl-βCD-PAA. The hydrogels were found to release both drugs by means of Fickian diffusion as the predominant mechanism. A slight trend toward negative correlation was found between the Ka and Higuchi kH values for DIF. These results highlight the potential of CD-PAA hydrogels to control the release of model drugs through inclusion complexation.
- Cyclodextrin-crosslinked poly(acrylic acid): adhesion and controlled release of diflunisal and fluconazole from solid dosage forms. [Journal Article, Research Support, Non-U.S. Gov't]
- AAPS PharmSciTech 2013 Mar; 14(1):301-11.
The controlled release of diflunisal and fluconazole from tablets made of novel polymers, poly(acrylic acid) (PAA) crosslinked with either β-cyclodextrin (βCD) or hydroxypropyl-βCD (HPβCD), was investigated and Carbopol 934P (Carbopol) was used as a highly crosslinked PAA for comparison. Diflunisal strongly associates with βCD-PAA and HPβCD-PAA polymers (Ka of 486 and 6,055 M(-1) respectively); thus, it was physically mixed into the conjugates and also precomplexed to identify whether decomplexation has any influence on release kinetics. Fluconazole has poor complexing ability (Ka of 34 M(-1) with HPβCD-PAA); thus, it was only tested as a physical mixture. Swelling and adhesion studies were conducted on all tablet combinations and adhesivity of the CD-PAA polymer tablets was maintained. Diflunisal release was much slower from HPβCD-PAA tablets than from βCD-PAA, suggesting that a higher degree of complexation retards release. The precomplexed diflunisal release was also slower than the physically mixed diflunisal of the corresponding conjugate. The release closely followed zero-order kinetics for HPβCD-PAA, but was more sigmoidal for βCD-PAA and especially Carbopol. Conversely, poorly associating fluconazole released in almost exactly the same way across both polymers and Carbopol, indicating that the release kinetics of poorly associating drugs are not influenced by the presence of cyclodextrins. In view of the varying profiles and release rates shown with diflunisal for the different polymers, the fluconazole data support the concept that adequate complexation can indeed modulate the release kinetics of drugs.
- Sensitive and Selective Determination of Diflunisal in Human Plasma by LC-MS. [JOURNAL ARTICLE]
- J Chromatogr Sci 2012 Nov 9.
A reliable and sensitive liquid chromatography-tandem mass spectrometry assay has been proposed for the selective determination of diflunisal in the presence of its glucuronide metabolites. The analyte and clofibric acid as internal standard (IS) are extracted from 50 µL of human plasma by solid-phase extraction. Chromatographic separation is conducted on a Prodigy ODS 3V column (150 × 4.6 mm, 5 µm) under isocratic conditions. The possible interference of acyl glucuronide and phenolic glucuronide, the two major inactive metabolites of diflunisal, is also checked in plasma samples. Detection of the analyte and IS is achieved by tandem mass spectrometry, operating in negative ionization and multiple reaction monitoring acquisition mode. The limits of detection and quantitation of the method are 0.10 and 1.00 µg/mL, respectively, with a linear dynamic range of 1.00-160 µg/mL for diflunisal. The intra-batch and inter-batch precision (percent coefficient of variation) is ≤4.2% and the mean recovery is >92% for diflunisal across quality control levels. The method is successfully applied to a bioequivalence study of a 500 mg diflunisal tablet formulation in 30 healthy Indian male subjects under fasting conditions. The reproducibility in the measurement of study data is demonstrated by the reanalysis of 120 incurred samples.
- Individual NSAIDs and upper gastrointestinal complications: a systematic review and meta-analysis of observational studies (the SOS project). [Journal Article, Meta-Analysis, Research Support, Non-U.S. Gov't, Review]
- Drug Saf 2012 Dec 1; 35(12):1127-46.
The risk of upper gastrointestinal (GI) complications associated with the use of NSAIDs is a serious public health concern. The risk varies between individual NSAIDs; however, there is little information on the risk associated with some NSAIDs and on the impact of risk factors. These data are necessary to evaluate the benefit-risk of individual NSAIDs for clinical and health policy decision making. Within the European Community's Seventh Framework Programme, the Safety Of non-Steroidal anti-inflammatory drugs (NSAIDs) [SOS] project aims to develop decision models for regulatory and clinical use of individual NSAIDs according to their GI and cardiovascular safety.The aim of this study was to conduct a systematic review and meta-analysis of observational studies to provide summary relative risks (RR) of upper GI complications (UGIC) associated with the use of individual NSAIDs, including selective cyclooxygenase-2 inhibitors.We used the MEDLINE database to identify cohort and case-control studies published between 1 January 1980 and 31 May 2011, providing adjusted effect estimates for UGIC comparing individual NSAIDs with non-use of NSAIDs. We estimated pooled RR and 95% CIs of UGIC for individual NSAIDs overall and by dose using fixed- and random-effects methods. Subgroup analyses were conducted to evaluate methodological and clinical heterogeneity between studies.A total of 2984 articles were identified and 59 were selected for data abstraction. After review of the abstracted information, 28 studies met the meta-analysis inclusion criteria. Pooled RR ranged from 1.43 (95% CI 0.65, 3.15) for aceclofenac to 18.45 (95% CI 10.99, 30.97) for azapropazone. RR was less than 2 for aceclofenac, celecoxib (RR 1.45; 95% CI 1.17, 1.81) and ibuprofen (RR 1.84; 95% CI 1.54, 2.20); 2 to less than 4 for rofecoxib (RR 2.32; 95% CI 1.89, 2.86), sulindac (RR 2.89; 95% CI 1.90, 4.42), diclofenac (RR 3.34; 95% CI 2.79, 3.99), meloxicam (RR 3.47; 95% CI 2.19, 5.50), nimesulide (RR 3.83; 95% CI 3.20, 4.60) and ketoprofen (RR 3.92; 95% CI 2.70, 5.69); 4-5 for tenoxicam (RR 4.10; 95% CI 2.16, 7.79), naproxen (RR 4.10; 95% CI 3.22, 5.23), indometacin (RR 4.14; 95% CI 2.91, 5.90) and diflunisal (RR 4.37; 95% CI 1.07, 17.81); and greater than 5 for piroxicam (RR 7.43; 95% CI 5.19, 10.63), ketorolac (RR 11.50; 95% CI 5.56, 23.78) and azapropazone. RRs for the use of high daily doses of NSAIDs versus non-use were 2-3 times higher than those associated with low daily doses.We confirmed variability in the risk of UGIC among individual NSAIDs as used in clinical practice. Factors influencing findings across studies (e.g. definition and validation of UGIC, exposure assessment, analysis of new vs prevalent users) and the scarce data on the effect of dose and duration of use of NSAIDs and on concurrent use of other medications need to be addressed in future studies, including SOS.
- Stability of the transthyretin molecule as a key factor in the interaction with a-beta peptide--relevance in Alzheimer's disease. [Journal Article, Research Support, Non-U.S. Gov't]
- PLoS One 2012; 7(9):e45368.
Transthyretin (TTR) protects against A-Beta toxicity by binding the peptide thus inhibiting its aggregation. Previous work showed different TTR mutations interact differently with A-Beta, with increasing affinities correlating with decreasing amyloidogenecity of the TTR mutant; this did not impact on the levels of inhibition of A-Beta aggregation, as assessed by transmission electron microscopy. Our work aimed at probing differences in binding to A-Beta by WT, T119M and L55P TTR using quantitative assays, and at identifying factors affecting this interaction. We addressed the impact of such factors in TTR ability to degrade A-Beta. Using a dot blot approach with the anti-oligomeric antibody A11, we showed that A-Beta formed oligomers transiently, indicating aggregation and fibril formation, whereas in the presence of WT and T119M TTR the oligomers persisted longer, indicative that these variants avoided further aggregation into fibrils. In contrast, L55PTTR was not able to inhibit oligomerization or to prevent evolution to aggregates and fibrils. Furthermore, apoptosis assessment showed WT and T119M TTR were able to protect against A-Beta toxicity. Because the amyloidogenic potential of TTR is inversely correlated with its stability, the use of drugs able to stabilize TTR tetrameric fold could result in increased TTR/A-Beta binding. Here we showed that iododiflunisal, 3-dinitrophenol, resveratrol, [2-(3,5-dichlorophenyl)amino] (DCPA) and [4-(3,5-difluorophenyl)] (DFPB) were able to increase TTR binding to A-Beta; however only DCPA and DFPB improved TTR proteolytic activity. Thyroxine, a TTR ligand, did not influence TTR/A-Beta interaction and A-Beta degradation by TTR, whereas RBP, another TTR ligand, not only obstructed the interaction but also inhibited TTR proteolytic activity. Our results showed differences between WT and T119M TTR, and L55PTTR mutant regarding their interaction with A-Beta and prompt the stability of TTR as a key factor in this interaction, which may be relevant in AD pathogenesis and for the design of therapeutic TTR-based therapies.