Co-drug of isoniazid and sulfur containing antioxidant for attenuation of hepatotoxicity and treatment of tuberculosis.

The prolonged use of isoniazid (INH) - a highly effective drug in the treatment of tuberculosis - causes fatal liver injury. In order to overcome this adverse effect, a unique amide codrug was designed by covalently linking INH with sulfur-containing antioxidant- alpha-lipoic acid for possible hepatoprotective and antimycobacterial effect. Co-drug LI was prepared by Schotten Baumann reaction and was characterized by spectroscopic analysis. To check the bioreversibility of LI, in vitro release tests were conducted in buffers of specific pH, stomach, and intestinal homogenates of rat employing HPLC. Male Wistar rats were used for the evaluation of the hepatoprotective activity. Liver function markers, oxidative stress markers, and biochemical parameters were estimated. The antimycobacterial efficacy of LI was examined in terms of its ability to decrease the lung bacillary load in Balb/c mice infected intravenously with Mycobacterium tuberculosis. LI resisted hydrolysis in buffers of pH 1.2 (acidic), pH 7.4 (basic), and stomach homogenate of the rat while displayed significant hydrolysis (88.19%) in intestinal homogenates over a period of 6 h. The effect of LI on liver function, antioxidant and biochemical paradigms was remarkable as it reestablished the enzyme levels and restored hepatic cytoarchitecture representing its abrogating effect. The findings of antimycobacterial activity assessment evidently demonstrated that LI was as potent as INH in lowering the mycobacterial load in mice. The outcome of this exploration confirmed that the described co-drug can offer desirable safety and therapeutic benefit in the management of tuberculosis.

Phenolic acid-tethered isoniazid for abrogation of drug-induced hepatotoxicity: design, synthesis, kinetics and pharmacological evaluation.

Morphological and metabolic aberrations in the liver caused by long-term use of anti-tubercular agent isoniazid (INH) have been an issue of great concern in tuberculosis treatment. To resolve this issue, a novel hepatoprotective prodrug strategy was developed by combining the antioxidant property of phenolic acids with INH moiety for probable synergistic effect. In this work, INH was conjugated with phenolic antioxidants using Schotten-Baumann reaction through biocleavable amide linkage. Synthesized prodrugs were characterized by spectral analysis and in vitro release studies were carried out using HPLC. They were found to be stable in acidic (pH 1.2), basic (pH 7.4) buffers, stomach homogenates of rat whereas hydrolyzed significantly (56.03-88.62%) in intestinal homogenates over a period of 6 h. Further their hepatoprotective potential was evaluated in male Wistar rats by performing liver function tests, oxidative stress markers, and histopathology studies. All the prodrugs were effective in abating oxidative stress and re-establishing normal hepatic physiology. Especially the effect of prodrugs of INH with gallic acid and syringic acid in restoring levels of enzymes superoxide dismutase and glutathione peroxidase and abrogating liver damage was noteworthy. The findings of this investigation demonstrated that reported prodrugs can add safety and efficacy to future clinical protocols of tuberculosis treatment.

Investigation of mitigating effect of colon-specific prodrugs of boswellic acid on 2,4,6-trinitrobenzene sulfonic acid-induced colitis in Wistar rats: Design, kinetics and biological evaluation.

AIM: To develop a colon-targeting bioreversible delivery system for ß-boswellic acid (BBA) and explore utility of its prodrugs in 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis in rats. METHODS: Synthesis of 4 co-drugs of BBA with essential amino acids was achieved by CDI coupling, followed by their spectral characterization. In vitro kinetics were studied by HPLC in aqueous buffers, homogenates of gastrointestinal tract and fecal matter. In vivo kinetic studies were performed in Wistar rat plasma, urine and feces. The prodrugs were screened in TNBS-induced colitis modeled Wistar rats. Statistical significance was assumed at P < 0.05, P < 0.01, P < 0.001 when compared with disease controls using one-way and two-way ANOVAs. RESULTS: Prodrugs were stable in 0.05 mol/L HCl buffer (pH 1.2) and stomach homogenates. Negligible hydrolysis was observed in phosphate buffer and intestinal homogenates. Substantial release (55%-72% and 68%-86%) of BBA was achieved in rat fecal matter and homogenates of colon. In vivo studies of BBA with L-tryptophan (BT) authenticated colon-specific release of BBA. But, surprisingly substantial concentration of BBA was seen to reach the systemic circulation due to probable absorption through colonic mucosa. Site-specifically enhanced bioavailability of BBA could be achieved in colon, which resulted in demonstration of significant mitigating effect on TNBS-induced colitis in rats without inducing any adverse effects on stomach, liver and pancreas. Prodrug of BT was found to be 1.7% (P < 0.001) superior than sulfasalazine in reducing the inflammation to colon among all prodrugs tested. CONCLUSION: The outcome of this study strongly suggests that these prodrugs might have dual applicability to inflammatory bowel disease and chronotherapy of rheumatoid arthritis.

Investigating Drug Repositioning Approach to Design Novel Prodrugs for Colon-specific Release of Fexofenadine for Ulcerative Colitis.

BACKGROUND: Recent immunologic data implicates involvement of mucosal immune cells of the intestine like eosinophils and mast cells to be functionally involved in the pathogenesis of UC. Mast cell activation is followed by increased secretion and elevated tissue concentration of histamine. Inhibition of mucosal histamine release in colon may be an effective therapeutic approach to treat UC. Some studies report that intestinal inflammation associated with acute and chronic colitis has been ameliorated by fexofenadine in mice. OBJECTIVE: In the present work, we investigated the effect of colon- specific prodrugs of antihistaminic fexofenadine on TNBS- induced colitis in Wistar rats, applying the principle of drug repositioning. METHOD: Amino acid- appended amide prodrugs of fexofenadine were designed and characterized spectrally. In vitro kinetics and protective effect of prodrugs were studied on TNBS-induced colitis in Wistar rats. RESULTS: Conjugation with amino acids improved the hydrophilicity of fexofenadine (log P: 0.037 to 0.082) to enable efficient delivery to colon. Prodrugs were chemically and enzymatically stable in aqueous buffers (pH 1.2 and7.4) and stomach homogenates/intestinal homogenates, respectively. Prodrugs were substantially cleaved to release 60-70% of fexofenadine in homogenates of colon in 12 h. Prodrug of fexofenadine with L-glutamine additively and significantly suppressed TNBS-induced colitis showing comparable effects to orally administered 5-aminosalicylic acid. CONCLUSION: The outcome of this preliminary work emphasizes involvement of mast cells that release histamine as one of the important pathological inducers of UC. These promising, dual acting, colontargeting fexofenadine prodrugs could be explored further for repositioning fexofenadine in the treatment of UC and its relapse.

Novel Thioester Prodrug of N-acetylcysteine for Odor Masking and Bioavailability Enhancement.

BACKGROUND: The mucolytic N-acetylcysteine (NAC) is used to control the excessive mucus secretion if mucus is the underlying cause of broncho-constriction. Its major drawbacks are poor bioavailability due to extensive first pass effect, poor lipophilicity, high protein binding and offensive odor. METHODS: For minimizing above shortcomings of NAC, in present study thioester (A1) prodrug of NAC was synthesized by conventional as well as microwave-assisted methods. Release studies of A-1 were carried out using HPLC and pharmacological evaluation was performed in ovalbumin-induced model of pulmonary inflammation in Sprague dawley rats. RESULTS: A-1 was found to be stable in HCl buffer, phosphate buffer, stomach homogenates but furnished 30% NAC in 6h and 1.7% of NAC in 4h when incubated with small intestinal and liver homogenates respectively. Upon oral administration of A-1 to rats, 4.85% NAC was detected in blood at 8h. Urine samples pooled over a period of 24h exhibited 0.75% NAC while negligible concentration was found in 24 h pooled samples of feces. CONCLUSION: The findings of this preliminary investigation demonstrated significant effects of thioester prodrug A-1 as compared to NAC through reduction of lung inflammation, airway eosinophilia and reversal of lung function parameters in ovalbumin- challenged rats at half the equimolar dose of NAC. Interestingly masking thiol group through thioester formation resulted in odorless prodrug. We propose that thioester prodrug using palmitic acid as a carrier is a promising strategy to enhance bioavailability of NAC by increasing its lipophilicity/ absorption and minimizing its first pass metabolism.

Amide-linked Ethanolamine Conjugate of Gemfibrozil as a Profound HDL Enhancer: Design, Synthesis, Pharmacological Screening and Docking Study.

Elevated concentration of any or all types of lipids in the plasma including hypertriglyceridemia and hypercholesterolemia leads to atherosclerotic cardiovascular disease. Effective medication needs multiple drug therapy as recommended cholesterol and triglyceride levels are difficult to achieve by monotherapy and frequently require the use of more than one lipid-lowering medication. Gemfibrozil lowers plasma triglyceride-rich lipoproteins mainly VLDL and increases HDL. It is associated with short plasma half-life (1.5h) and GIT distress on long term use. In a study it was found that ethanolamine decreases serum cholesterol, especially VLDL cholesterol and LDL cholesterol in rats fed an HF/HC diet. In the present work, we thought of exploring the effect of co-drug of gemfibrozil with ethanolamine (GE-I) as a potential combination therapy for the management of mixed hyperlipidemia. Synthesis of GE-I was effected by CDI coupling. Structure was confirmed spectrally. Interestingly kinetic studies revealed that GE-I resisted chemical and enzymatic hydrolysis. In tritoninduced hyperlipidemia, significant lowering of serum lipid levels was observed. The hallmark of GEI was its profound effect on HDL level which was raised above the normal level by 15%. Docking study also supported modulatory effect of GE-I (docking score -7.012) on PPAR-α which was comparable to docking score of gemfibrozil (-9.432). These preliminary observations prompt us to consider GE-I as a novel, serendipitous, hybrid anti-hyperlipidemic new chemical entity which needs be studied extensively to prove it as an HDL enhancing anti-hyperlipidemic agent.

An update on disease modifying antirheumatic drugs.

Disease modifying antirheumatic drugs (DMARDs) is a category of drugs which is used as medication in various arthritic conditions to arrest the progression of disease along with relief from pain. About 83% of population worldwide uses DMARDs. Withdrawal of COX-2 inhibitors because of cardiovascular side effects and short-term action associated with glucocorticoids provided a motivation for development of newer DMARDs. Currently non- biological DMARDs like methotrexate, sulfasalazine, hydroxychloroquine and azathioprine serve the purpose of relieving pain and inhibiting the progression of disease. Biological DMARDs like toclizumab, adalimumab, infliximab, golimumab and abatacept have shown more efficacy and lesser side effects as compared to non- biological DMARDs but their access to patient is less because of higher cost. DMARDs act by different mechanisms against inflammation like inhibition of tumor necrosis factor, suppression of IL-1 and TNF-α, induction of apoptosis of inflammatory cells, by increasing chemotactic factors, inhibition of purine synthesis, pyrimidine metabolism or purine embolism. DMARDs have important applications in diseases like rheumatoid arthritis, Crohn's disease, juvenile idiopathic arthritis, psoriatic arthritis and myasthenia gravis. Present review mainly focuses on DMARDs and their clinical applications giving an overview of their mechanism of action, pharmacokinetic properties, advantages over conventional therapies, shortcomings and recent trends.

Colon-specific prodrugs of 4-aminosalicylic acid for inflammatory bowel disease.

Despite the advent of biological products, such as anti-tumor necrosis factor-α monoclonal antibodies (infliximab and adalimumab), for treatment of moderate to severe cases of inflammatory bowel disease (IBD), most patients depend upon aminosalicylates as the conventional treatment option. In recent years, the increased knowledge of complex pathophysiological processes underlying IBD has resulted in development of a number of newer pharmaceutical agents like low-molecular-weight heparin, omega-3 fatty acids, probiotics and innovative formulations such as high-dose, once-daily multi-matrix mesalamine, which are designed to minimize the inflammatory process through inhibition of different targets. Optimization of delivery of existing drugs to the colon using the prodrug approach is another attractive alternative that has been utilized and commercialized for 5-aminosalicylic acid (ASA) in the form of sulfasalazine, balsalazide, olsalazine and ipsalazine, but rarely for its positional isomer 4-ASA - a well-established antitubercular drug that is twice as potent as 5-ASA against IBD, and more specifically, ulcerative colitis. The present review focuses on the complete profile of 4-ASA and its advantages over 5-ASA and colon-targeting prodrugs reported so far for the management of IBD. The review also emphasizes the need for reappraisal of this promising but unexplored entity as a potential treatment option for IBD.

Rational design and development of colon-specific prodrugs.

Earlier colon was considered as a black-box, acting as a site for production and temporary storage of excreta and responsible for absorption of electrolytes and water. But, with the discovery of sulfasalazine as colon-specific prodrug, the promising and challenging issue of treating local pathologies was presented with colon as an organ of significance for target-specific delivery of drugs. The need and desirable attributes of colon-specific drug delivery systems have been well recognized, extensively explored and documented in the literature. The success of a colon-specific prodrug depends on its rational design and understanding the demands of the organ to be targeted and the delivery system to be developed. The present review mainly focuses on anatomy/physiology of colon, colonic microbiota, enzymatic set up of colon, pathophysiology of local diseases of colon, factors, obstacles and rationale for designing colon specific drug delivery system, various targets, potential drug candidates and novel colon-targeting carriers along with varied linkages that could be explored, merits and demerits of this design and recent trends in this field. Brief review of methodologies for characterization and in vitro/in vivo release studies is presented. The available animal models with quantifying parameters for evaluating colon-targeting potential and effectiveness of the colon-specific prodrugs for inflammatory bowel disease is also included in this review.

Prodrug strategies for antihypertensives.

There is a great emphasis on research to discover methods aimed at enhancing the efficacy of drugs and reducing their toxicity and unwanted side effects. Prodrugs are biologically inactive compounds that are converted to actual drug molecule, through biotransformation, that combine with the receptors to produce the biological action. Prodrugs can thus be considered as drugs containing specialized nontoxic protective groups utilized in a transient manner to alter or eliminate the undesirable properties of the parent drug molecule. Hypertension is one of the leading risk factors for cardiovascular disease and represents a major health and economic burden. Most of the drugs for cardiovascular diseases have low oral bioavailability, short duration of action, first pass metabolism and variable lipohilicities. Out of the need to overcome these limitations, various prodrugs have been designed for antihypertensive agents. This review extensively focuses on various strategies used for design and development of prodrugs for the various classes of antihypertensives, emphasizing on the details regarding the need for prodrug synthesis for each class, structure, type of modification and goal achieved. It also provides an insight into the major advances in the field of antihypertensive prodrug research.

Synthesis, kinetic studies and pharmacological evaluation of mutual azo prodrugs of 5-aminosalicylic acid for colon-specific drug delivery in inflammatory bowel disease.

Colon-specific mutual azo prodrugs of 5-aminosalicylic acid with essential amino acids were synthesized for the management of inflammatory bowel disease. The structures were confirmed by elemental and spectral analyses. 85-88% release of 5-aminosalicylic acid was achieved in rat fecal matter with half-lives ranging from 140 to 160 min, following first order kinetics. The prodrugs exhibited comparable ameliorating effect as that of sulfasalazine on trinitrobenzenesulfonic acid-induced experimental colitis in rats with a better safety profile.

Colon-specific mutual amide prodrugs of 4-aminosalicylic acid for their mitigating effect on experimental colitis in rats.

Mutual amide prodrugs of 4-aminosalicylic acid with D-phenylalanine and L-tryptophan were synthesized for targeted drug delivery to the inflamed gut tissue in inflammatory bowel disease. Stability studies in aqueous buffers (pH 1.2 and 7.4) showed that the synthesized prodrugs were stable in both the buffers over a period of 10 h. In rat fecal matter the release of 4-aminosalicylic acid from the prodrugs was in the range of 86-91% over a period of 20 h, with half-lives ranging between 343 and 412 min following first order kinetics. Targeting potential of the carrier system and the ameliorating effect of the amide conjugates were evaluated in trinitrobenzenesulfonic acid-induced experimental colitis model in rats. The prodrugs were assessed for their probable damaging effects on pancreas and liver with the help of histopathological analysis and for their ulcerogenic potential by Rainsford's cold stress method. They were found to have improved safety profile than sulfasalazine, oral 4- and 5-aminosalicylic acid with similar pharmacological spectrum and advantages of sulfasalazine.

Development and validation of a HPTLC method for Estimation of Duloxetine Hydrochloride in Bulk Drug and in Tablet Dosage Form.

Duloxetine hydrochloride is a potent dual reuptake inhibitor of serotonin and norepinephrine used to treat major depressive disorders. The present work describes a simple, precise and accurate HPTLC method for its estimation as bulk and in tablet dosage form. The chromatographic separation was carried out on precoated silica gel 60 F254 aluminium plates using mixture of chloroform:methanol (8:1 v/v) as mobile phase and densitometric evaluation of spots was carried out at 235 nm using Camag TLC Scanner-3 with win CAT 1.3.4 version software. The experimental parameters like band size of the spot applied, chamber saturation time, solvent front migration, slit width etc. were critically studied and optimum conditions were evolved. The drug was satisfactorily resolved with Rf value 0.11+/-0.01. The accuracy and reliability of the proposed method was ascertained by evaluating various validation parameters like linearity (40-200 ng/spot), precision (intra-day RSD 0.46-0.75%, inter-day RSD 0.46-1.59%), accuracy (98.72+/-0.20) and specificity according to ICH guidelines. The proposed method can analyse ten or more formulation units simultaneously on a single plate and provides a faster and cost-effective quality control tool for routine analysis of duloxetine hydrochloride as bulk drug and in tablet formulation.

Colon-specific, mutual azo prodrug of 5-aminosalicylic acid with L-tryptophan: synthesis, kinetic studies and evaluation of its mitigating effect in trinitrobenzenesulfonic acid-induced colitis in rats.

Mutual azo prodrug of 5-aminosalicylic acid with l-tryptophan was synthesized by coupling l-tryptophan with salicylic acid, for targeted drug delivery to the inflamed gut tissue in inflammatory bowel disease. The structure of synthesized prodrug was confirmed by elemental analysis, IR and NMR spectroscopy. In vitro kinetic studies in HCl buffer (pH 1.2) showed negligible release of 5-aminosalicylic acid, whereas in phosphate buffer (pH 7.4) 18% release was observed over a period of 7 h. In rat fecal matter, 87.9% of 5-aminosalicylic acid was released with a half-life of 143.6 min, following first order kinetics. The azo conjugate was evaluated for its ulcerogenic potential by Rainsford's cold stress method. The ameliorating effect of the azo conjugate and therapeutic efficacy of the carrier system was evaluated in trinitrobenzenesulfonic acid-induced experimental colitis model. The synthesized prodrug was found to be equally effective in mitigating the colitis in rats as that of sulfasalazine without the ulcerogenicity of 5-aminosalicylic acid.

Synthesis, kinetic studies and pharmacological evaluation of mutual azo prodrug of 5-aminosalicylic acid with D-phenylalanine for colon specific drug delivery in inflammatory bowel disease.

Mutual azo prodrug of 5-aminosalicylic acid with d-phenylalanine was synthesized by coupling D-phenylalanine with salicylic acid, for targeted drug delivery to the inflamed gut tissue in inflammatory bowel disease. The structure of synthesized prodrug was confirmed by elemental analysis, IR and NMR spectroscopy. In vitro kinetic studies in HCl buffer (pH 1.2) showed negligible release of 5-aminosalicylic acid, whereas in phosphate buffer (pH 7.4) only 15% release was observed over a period of 7h. In rat fecal matter the release of 5-aminosalicylic acid was almost complete (85%), with a half-life of 160.1 min, following first order kinetics. The azo conjugate was evaluated for its ulcerogenic potential by Rainsford's cold stress method. Therapeutic efficacy of the carrier system and the mitigating effect of the azo conjugate were evaluated in trinitrobenzenesulfonic acid-induced experimental colitis model. The synthesized prodrug was found to be equally effective in mitigating the colitis in rats as that of sulfasalazine without the ulcerogenicity of 5-aminosalicylic acid.

Synthesis, kinetic studies and pharmacological evaluation of mutual azo prodrug of 5-aminosalicylic acid for colon-specific drug delivery in inflammatory bowel disease.

Mutual azo prodrug of 5-aminosalicylic acid with l-tyrosine was synthesized by coupling l-tyrosine with salicylic acid, for targeted drug delivery to the inflamed gut tissue in inflammatory bowel disease. The structure was confirmed by elemental analysis, IR and NMR spectroscopy. In vitro kinetic studies in rat fecal matter showed 87.18% release of 5-aminosalicylic acid with a half-life of 140.28min, following first order kinetics. Therapeutic efficacy of the carrier system and the mitigating effect of the azo conjugate were evaluated in trinitrobenzenesulfonic acid-induced experimental colitis model. Myeloperoxidase activity was determined by the method of Krawisz et al. The synthesized prodrug was found to produce comparable mitigating effect as that of sulfasalazine on colitis in rats.