Synthesis, stability studies, anti-inflammatory activity and ulcerogenicity of morpholinoalkyl ester prodrugs of niflumic acid

In search for potential prodrugs for anti-inflammatory drug candidates in the niflumate series, novel morpholinoalkyl ester prodrugs of niflumic acid (CAS 4394-00-7) 5a-b were prepared by esterification of appropriate morpholinylalkyl alcohols 3a-b with niflumic acid 4 in the presence of dicyclohexyl carbodiimide (DCC) and catalyst dimethylamino pyridine (DMAP) at 0-5 degrees C. The structures were confirmed by elemental and spectral data (UV, IR, 1H-NMR, 13C-NMR, and EI-MS). The ester prodrugs 5a-b showed better solubility than the parent drug niflumic acid 4 in simulated gastric fluid (SGF) and phosphate buffer (pH 7.4). The in vitro hydrolysis studies were conducted at pH 1.3 (SGF), phosphate buffer (pH 7.4) and in human plasma diluted with phosphate buffer (pH 7.4) at 37+/-0.5 degrees C using HPLC with UV detection. The ester prodrugs 5a-b were quantitatively hydrolyzed to the parent drug niflumic acid 4 by enzymatic and/or chemical means. It is observed that an increase in the carbon chain length rendered the prodrugs 5a-b more stable in phosphate buffer (pH 7.4) than in pH 1.3 (SGF), but they were rapidly hydrolyzed in human plasma at 37+/-0.5 degrees C. They exhibited longer hydrolytic half-lives of 16.11-53.30 h in aqueous buffer solutions (pH 1.3 and 7.4) and 1.63-2.73 min in human plasma, respectively. The title compounds were evaluated in vivo for anti-inflammatory activity in carrageenan induced rat paw oedema model in rats at the doses 45, 90, 150 mg/kg b.w. The test compounds exhibited good anti-inflammatory activity (46.6-53.2 % at the dose of 150 mg/kg b. w.) with respect to niflumic acid (78.7 % at the dose of 90 mg/kg b.w.). The compounds were also screened for in vivo ulcerogenicity, it was observed that the prodrug 5b was significantly less irritating to gastric mucosa than compound 5a and the parent drug niflumic acid 4 following single and chronic oral administration in rats.     

Pharmacoeconomics of nonsteroidal anti-inflammatory drugs (NSAIDs)

Nonsteroidal anti-inflammatory drugs (NSAIDs) are widely used for the relief of the symptoms of osteoarthritis (OA), rheumatoid arthritis (RA), sprains and strains, sports injuries and menstrual disorders, and have a small role in the management of patent ductus arteriosus in the neonate. In patients with RA, symptom relief through use of NSAIDs is firmly established, although it remains unclear whether they influence the course and outcome of the disease. For the average patient with RA taking NSAIDs, the attributable risk of hospitalisation with gastrointestinal problems related to NSAIDs is 1.3 to 1.6% annually and risk of death is 0.15%. Associations of therapy with risk are greatest with age, corticosteroid use and previous NSAID-related gastrointestinal adverse effects, and less marked with disability and high NSAID dose. These are important data in attempting to balance risk of therapy with clinical efficacy in an individual patient, and assessing the cost-effectiveness of prophylaxis. Although half of all NSAID consumption is for control of pain associated with degenerative conditions, their superiority over simple analgesics in osteoarthritis is poorly documented. This finding supports the use of the simple analgesic paracetamol (acetaminophen) as the preferred therapy of osteoarthritis, especially when its lower cost and low incidence of adverse effects are taken into consideration. Consistent differences in clinical effectiveness of individual NSAIDs have not been demonstrated, although unpredictable interpatient variation in response to individual agents is of considerable clinical importance, and a more expensive NSAID may prove cost effective for some patients. Cost effectiveness can be improved by a self-adjusted dosage regime which also leads to lower overall drug consumption. The adverse gastrointestinal effects of these drugs account for about 30% of the overall cost of arthritis treatment, and although studies to date have been too limited to assess the relative risk of gastrointestinal toxicity of the different NSAIDs reliably, ibuprofen appears to be one of the least hazardous, and azapropazone one of the most hazardous. Although the effectiveness of prophylaxis with H 2-antagonists and with prostaglandin E 1 analogues (prostaglandin-E 1 analogues) has been established, estimates of cost-benefit ratios are widely divergent. To establish the most cost-effective therapy with NSAIDs, more data are required to establish multivariable risk profiles for identification of patients at particular risk, the optimal drug, and its optimal dosage and duration of treatment.(ABSTRACT TRUNCATED AT 400 WORDS)     

Hypersensitivity to aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs)

Hypersensitivity to aspirin and other non steroidal anti-inflammatory drugs (NSAIDs) manifesting in the airways (rhinosinusitis, polyps, asthma) or in the skin (urticaria, angioedema) is the second most frequent untoward allergic reaction to drugs. Various aspects of this syndrome, such as its clinical features, the cell types and mediators involved, the role of underlying chronic inflammatory processes, the patterns of cross-reactivity between NSAIDs, the major role of sulfidoleukotrienes (LTC4) and of some other mediators such as prostaglandin E2 (PGE2) and C5a are briefly reviewed. It has been assumed for a long time that there were no reliable in vitro tests for that condition and that diagnostic confirmation can only be ascertained by provocation challenge. This appears no longer to be true, since several recent studies using a leukotriene release test (CAST) or a basophil activation test (BAT) on blood basophils, or a combination of both tests, yields positive results (70-75%) in a sizeable number of clinically validated cases, with a high specificity (above 85%). The finding in that syndrome of hyperreactive basophils suggests that the NSAID hypersensitivity syndrome is due to the associated effect of several factors: 1) Localized inflammatory processes causing a non specific cellular hyperreactivity; 2) An abnormal pharmacogenetic reaction to NSAIDs resulting in a hyperproduction of LTC4 and other mediators by activated mast cells, basophils and eosinophils.     

Vasorelaxant effect of nitric oxide releasing steroidal and nonsteroidal anti-inflammatory drugs

The effect of several nitric oxide releasing-non-steroidal anti-inflammatory drugs (NO-NSAID) and nitroprednisolone on blood vessel relaxation in vitro and in vivo was studied. Nitroflurbiprofen (NOF; EC(50), 688.8+/-93.8 microM), nitroaspirin (NOA; EC(50), 57.9+/-6.5 microM), nitroparacetamol (NOPARA; EC(50), 71.5+/-14.6 microM) and nitroprednisolone (EC(50), 15.1+/-1.4 microM) caused concentration-related relaxation of noradrenaline (NA)-contracted rat aortic rings. All NO releasing compounds tested were approximately three orders of magnitude less potent than sodium nitroprusside (SNP, EC(50), 35.7+/-3.5 nM). The vasorelaxant effect of NOF and NOPARA in the rat aorta was potentiated by zaprinast (5 microM) and reduced by ODQ (5 microM). Flurbiprofen and paracetamol (100 microM) caused minimal (<10%) relaxation of the rat aorta and did not affect the response to SNP. The effect of NOF was unchanged in the presence of L-NAME (100 microM; EC(30), 181.8+/-35.1 microM cf. EC(30), 125.1+/-17.0 microM, P>0.05) but increased by removal of the endothelium (EC(30), 164.3+/-26.3 microM cf. EC(50), 688.8+/-93.8 microM, P<0.05). NOF (0.1 - 50 microM) produced a small but not concentration-related vasodilation of the NA-preconstricted (i.e. "high tone") perfused rat mesentery preparation (cf. SNP, EC(30), 4.4+/-0.7 microM). In contrast, NOF (1 - 100 microM) produced concentration-related vasodilation of the "high tone" perfused rat kidney with an EC(50) of 33.1+/-4.4 microM. Neither NOF (74 mg kg(-1), i.p.) nor NOA (91.9 mg kg(-1), i.p.) nor equimolar doses of flurbiprofen (50 mg kg(-1), i.p.) or aspirin (50 mg kg(-1), i.p.) affected mean arterial blood pressure (MAP) or heart rate (HR) of pentobarbitone-anaesthetized rats over a 1 h period. NO-NSAID relax blood vessels in vitro by an NO-dependent mechanism. The absolute vasorelaxant effect of NO releasing drug varies greatly with the choice of compound and between blood vessel preparations.     

Novel nonsteroidal antiinflammatory drugs possessing a nitric oxide donor diazen-1-ium-1,2-diolate moiety: design, synthesis, biological evaluation, and nitric oxide release studies

A novel group of hybrid nitric oxide-releasing nonsteroidal antiinflammatory drugs ((*)NO-NSAIDs) possessing a 1-(pyrrolidin-1-yl)diazen-1-ium-1,2-diolate (11, 13, 15) or 1-(N,N-dimethylamino)diazen-1-ium-1,2-diolate (12, 14, 16) moiety attached via a one-carbon methylene spacer to the carboxylic acid group of the traditional NSAIDs aspirin, ibuprofen, and indomethacin were synthesized. Although none of these ester prodrugs (11-16) exhibited in vitro cyclooxygenase (COX) inhibitory activity against the COX-1 and COX-2 isozymes (IC(50) > 100 microM), all of the compounds (11-16) significantly decreased carrageenan-induced rat paw edema. In this regard, the ester prodrugs 11-16 showed equipotent antiinflammatory activities in vivo to that of the parent drugs aspirin, ibuprofen, and indomethacin. All of the compounds released nitric oxide upon incubation with either phosphate buffer solution at pH 7.4 (14-16% range) or porcine liver esterase (16-19% range), but the percentage of (*)NO released was up to sixfold higher (93%) when these ester prodrugs were incubated with guinea pig serum. These incubation studies suggest that both (*)NO and the parent NSAID would be released upon in vivo cleavage by nonspecific serum esterases. The simultaneous release of aspirin and nitric oxide from the (*)NO-aspirin prodrugs constitutes a potentially beneficial property for the prophylactic prevention of thrombus formation and adverse cardiovascular events such as stroke and myocardial infarction. The data acquired in an in vivo ulcer index (UI) assay showed that for this group of ester prodrugs, particularly the (*)NO-aspirins (11, 12) and (*)NO-ibuprofens (13, 14), no lesions were observed (UI = 0) when compared to the parent drugs aspirin (UI = 57, 250 mg/kg po dose), ibuprofen (UI = 45, 250 mg/kg po dose), or indomethacin (UI = 34, 30 mg/kg po dose) at equivalent doses. Accordingly, these hybrid (*)NO-NSAID prodrugs possessing a diazen-1-ium-1,2-diolate moiety, represent a new approach for the rational design of antiinflammatory drugs with reduced gastric ulcerogenicity.     

Disturbance of menstruation as a side-effect of nonsteroidal anti-inflammatory drugs (NSAIDs)

Menstrual disturbances are not a generally recognized side-effect of non-steroidal antiinflammatory drugs (NSAIDs). Five case reports to the Netherlands Pharmacovigilance Foundation LAREB concern menstrual disturbances in suspected connection with the use of an NSAID. In one patient at several occasions the use of naproxen for dysmenorrhoea was followed by interruption of menstruation. In four other women the use of diclofenac, indomethacin or naproxen was followed by hypo- or amenorrhoea of one cycle duration. Prostaglandins play a complex role in the physiology of menstruation. The effects of NSAIDs on cyclo-oxygenase and prostaglandin metabolism may explain the observed disturbances of menstruation. Female patients of child-bearing age using an NSAID — either to treat dysmenorrhea or for other reasons — should be aware of the possibility of interruption, delay, decrease or missing of a menstrual period.     

Immunomodulatory effect of nonsteroidal anti-inflammatory drugs (NSAIDs) at the clinically available doses

Non-steroidal anti-inflammatory drugs (NSAIDs) with cyclooxygenase (COX) inhibitory activity are commonly used in various inflammatory diseases. In this study, to examine the immunomodulatory effects of well known NSAIDs at clinically available doses, macrophage- and T cell-mediated immune responses such as tumor necrosis factor (TNF)-alpha release and nitric oxide (NO) production, cell-cell adhesion, phagocytic uptake and lymphocyte proliferation were investigated. NSAIDs tested significantly enhanced TNF-alpha release from lipopolysaccharide (LPS)-activated RAW264.7 cells at certain concentrations (fenoprofen, indomethacin, piroxicam, aceclofenac, diclofenac and sulindac) or in a dose-dependent manner (aspirin and phenylbutazone). Of NSAIDs, phenylbutazone and aspirin most potently attenuated NO production, although sulindac was the only compound with cytoprotective activity against LPS-induced cytotoxicity. Most NSAIDs used displayed weak or no modulatory effects on phagocytic uptake and CD29- or CD43-mediated cell-cell adhesion. Interestingly, however, phenylbutazone itself triggered cell-cell clustering under normal culture conditions and enhanced the phagocytic activity. Aspirin and phenylbutazone also dose-dependently attenuated CD4+ T cell proliferation stimulated by concanavalin A (Con A) and CD8+ CTLL-2 cell proliferation induced by interleukin (IL)-2. Sulindac only blocked CTLL-2 cell proliferation. These results suggest that NSAIDs may differentially exert immunomodulatory effects on activated macrophages and lymphocytes, and some of the effects may enforce NSAID's therapeutic effect against inflammatory symptoms.     

Acute studies on safety index of nonsteroidal anti-inflammatory drugs in rats

Nonsteroidal anti-inflammatory drugs (NSAIDs) are commonly used to treat pain and inflammation. Their use is frequently limited by gastrointestinal side effects, ranging from dyspeptic symptoms to life threatening bleeding or perforations of gastroduodenal ulcers. The present study mainly aimed to establish a safety index of NSAIDs in experimental animals. Safety index is based on the ratio of ulcerogenic dose (UD₅₀) and anti-inflammatory dose (ED₅₀). The safety index of preferential COX-2 inhibitor (nimesulide, meloxicam) was investigated using carrageenan-induced paw oedema and acute ulcerogenic model in rats, compared with the classical NSAIDs (naproxen, indomethacin). Meloxicam was found to be the most potent NSAID (ED₅₀ 1.07 mg/kg, p.o.) followed by nimesulide (2.42 mg/kg, p.o.), indomethacin (2.72 mg/kg, p.o.) and naproxen (6.82 mg/kg, p.o.) after 240 min of carrageenan challenge. In acute ulcerogenic study naproxen, indomethacin and meloxicam were found to be ulcerogenic at lower doses (UD₅₀ 14.0, 3.80 and 3.21 mg/kg, p.o.) in comparison to nimesulide (UD₅₀ 24.52 mg/kg, p.o.). Meloxicam, naproxen and indomethacin also produced damage to gastric epithelium (disruption of mucus layer and damage to parietal cells) at ED₅₀ dose level when it was viewed under scanning electron microscope, but nimesulide did not distrub gastric mucosal integrity at ED₅₀ dose. Based on the safety index (Ulcerogenic dose₅₀ /Effective anti-inflammatory dose₅₀) the order of safety of these agents was nimesulide > meloxicam > naproxen > indomethacin.     

Effects of nitric oxide-releasing nonsteroidal anti-inflammatory drugs (NONO-NSAIDs) on melanoma cell adhesion

A new class of nitric oxide (NO•)-releasing nonsteroidal anti-inflammatory drugs (NONO-NSAIDs) were developed in recent years and have shown promising potential as NSAID substitutes due to their gentle nature on cardiovascular and gastrointestinal systems. Since nitric oxide plays a role in regulation of cell adhesion, we assessed the potential use of NONO-NSAIDs as anti-metastasis drugs. In this regard, we compared the effects of NONO-aspirin and a novel NONO-naproxen to those exerted by their respective parent NSAIDs on avidities of human melanoma M624 cells. Both NONO-NSAIDs, but not the corresponding parent NSAIDs, reduced M624 adhesion on vascular cellular adhesion molecule-1 (VCAM-1) by 20-30% and fibronectin by 25-44% under fluid flow conditions and static conditions, respectively. Only NONO-naproxen reduced (~ 56%) the activity of β1 integrin, which binds to α4 integrin to form very late antigen-4 (VLA-4), the ligand of VCAM-1. These results indicate that the diazeniumdiolate (NO•)-donor moiety is critical for reducing the adhesion between VLA-4 and its ligands, while the NSAID moiety can impact the regulation mechanism of melanoma cell adhesion.     

Radioprotection: the non-steroidal anti-inflammatory drugs (NSAIDs) and prostaglandins

Clinical and experimental studies of the acute and late effects of radiation on cells have enhanced our knowledge of radiotherapy and have led to the optimisation of radiation treatment schedules and to more precise modes of radiation delivery. However, as both normal and cancerous tissues have similar response to radiation exposure, radiation-induced injury on normal tissues may present either during, or after the completion of, the radiotherapy treatment. Studies on both NSAIDs and prostaglandins have indeed shown some evidence of radioprotection. Both have the potential to increase the survival of cells but by entirely different mechanisms. Studies of cell kinetics reveal that cells in the mitotic (M) and late G2 phases of the cell cycle are generally most sensitive to radiation compared with cells in the early S and G1/G0 phases. Furthermore, radiation leads to a mitotic delay in the cell cycle. Thus, chemical agents that either limit the proportion of cells in the M and G2 phases of the cell cycle or enhance rapid cell growth could in principle be exploited for their potential use as radioprotectors to normal tissue during irradiation. NSAIDs have been shown to exert anti-cancer effects by causing cell-cycle arrest, shifting cells towards a quiescence state (G0/G1). The same mechanism of action was observed in radioprotection of normal tissues. An increase in arachidonic acid concentrations after exposure to NSAIDs also leads to the production of an apoptosis-inducer ceramide. NSAIDs also elevate the level of superoxide dismutase in cells. Activation of heat shock proteins by NSAIDs increases cell survival by alteration of cytokine expression. A role for NSAIDs with respect to inhibition of cellular proliferation possibly by an anti-angiogenesis mechanism has also been suggested. Several in-vivo studies have provided evidence suggesting that NSAIDs may protect normal tissues from radiation injury. Prostaglandins do not regulate the cell cycle, but they do have a variety of effects on cell growth and differentiation. PGE(2) mediates angiogenesis, increasing the supply of oxygen and nutrients, essential for cellular survival and growth. Accordingly, PGE(2) at sufficiently high plasma concentrations enhances cellular survival by inhibiting pro-inflammatory cytokines such as TNF-alpha and IL-1beta. Thus, PGE(2) acts as a modulator, rather than a mediator, of inflammation. Prospective studies have suggested the potential use of misoprostol, a PGE(1) analogue, before irradiation, in prevention of radiation-induced side effects. The current understanding of the pharmacology of NSAIDs and prostaglandins shows great potential to minimise the adverse effects of radiotherapy on normal tissue.     

COX-2 inhibition, apoptosis, and chemoprevention by nonsteroidal anti-inflammatory drugs

Non-steroidal anti-inflammatory drugs (NSAIDs) have as their common mechanism the inhibition of cyclooxygenase (COX) enzymes, of which two isoforms (COX-1 and COX-2) exist. The effect of NSAIDs on chemoprevention and tumor regression has been shown in animal models, epidemiologic studies, and in treatment of patients. The exact biochemical and cellular mechanisms underlying each of these phenomena is only partially understood. Processes that have been recently implicated as being important include the inhibition of tumor cell growth, prevention of angiogenesis, and induction of apoptosis in neoplastic cells.     

Second-generation aspirin and indomethacin prodrugs possessing an O(2)-(acetoxymethyl)-1-(2-carboxypyrrolidin-1-yl)diazenium-1,2-diolate nitric oxide donor moiety: design, synthesis, biological evaluation, and nitric oxide release studies

The carboxylic acid group of the anti-inflammatory (AI) drugs aspirin and indomethacin was covalently linked to the 1-(2-carboxypyrrolidin-1-yl)diazen-1-ium-1,2-diolate ion via a one-carbon methylene spacer to obtain two new hybrid prodrugs. The aspirin prodrug ( 23) was a 2.2-fold more potent AI agent than aspirin, whereas the indomethacin prodrug ( 26) was about 1.6-fold less potent than indomethacin. Prodrugs 23 and 26 slowly released nitric oxide (NO) upon dissolution in phosphate buffer at pH 7.4 (1.1 mol of NO/mol of compound after 43 h), but the rate and the extent of NO release were higher (1.9 mol of NO/mol of compound in 3 min or less) when the compounds were incubated in the presence of porcine liver esterase. In vivo ulcer index (UI) studies showed that the aspirin prodrug 23 (UI = 0.7) and indomethacin prodrug 26 (UI = 0) were substantially less ulcerogenic than the parent drugs aspirin (UI = 51) and indomethacin (UI = 64).     

Nitric oxide release is not required to decrease the ulcerogenic profile of nonsteroidal anti-inflammatory drugs

The objective of this work was to evaluate the biological properties of a new series of nitric oxide-releasing nonsteroidal anti-inflammatory drugs (NO-NSAIDs) possessing a tyrosol linker between the NSAID and the NO-releasing moiety (PROLI/NO); however, initial screening of ester intermediates without the PROLI/NO group showed the required (desirable) efficacy/safety ratio, which questioned the need for NO in the design. In this regard, NSAID ester intermediates were potent and selective COX-2 inhibitors in vitro, showed equipotent anti-inflammatory activity compared to the corresponding parent NSAID, but showed a markedly reduced gastric toxicity when administered orally. These results provide complementary evidence to challenge the currently accepted notion that hybrid NO-NSAIDs exert their cytoprotective effects by releasing NO. Results obtained in this work constitute a good body of evidence to initiate a debate about the future replacement of NSAID prodrugs for unprotected NSAIDs (possessing a free carboxylic acid group) currently in clinical use.     

Synthesis and evaluation of anti-inflammatory, analgesic, ulcerogenicity and nitric oxide-releasing studies of novel ibuprofen analogs as nonulcerogenic derivatives

Since the last 41?years, Ibuprofen has been one of the most widely used Non-Steroidal Anti-Inflammatory Drug (NSAID) due to its anti-inflammatory actions. As all the NSAIDs are suffering from the deadlier GI toxicities, Ibuprofen also is no exception to these toxicities. The free ?CCOOH group is thought to be responsible for the Gastrointestinal (GI) tract toxicity associated with all the traditional NSAIDs. Therefore, the main aim of this study was to develop new chemical entities as potential anti-inflammatory agents with less GI toxicities. In this article, synthesis of a series of Hybrid molecules containing important pharmacophore of Ibuprofen and substituted diaryl rings on 5-membered heterocycle similar to coxibs and Nitric oxide-releasing moiety are described. All the synthesized compounds were tested in vivo for their anti-inflammatory, analgesic, ulcerogenic properties, and histopathological studies and in vitro for their nitric oxide-releasing properties. Out of the six synthesized compounds, four compounds showed significant anti-inflammatory and analgesic activity which was compared with standard. All the synthesized compounds exhibited significant nitric oxide-releasing and reduced GI ulcerogenic activity.     

三环苦参酯类前药的设计、合成及其药动学研究

目的设计合成全新三环苦参酯类前药衍生物,旨在改善其体内药动学行为。方法以苦参碱为原料,经碱水解开环、羧基成酯、12N-苄基取代、甲酯还原得到三环苦参醇母体化合物。采用两种前药制备策略,合成11个酯类前药和2个含有二硫键的前药化合物。选用SD大鼠测定化合物的口服药动学(PK)参数。结果与结论合成了13个未见文献报道的全新结构的三环苦参酯类前药,其结构经HR-MS、~1H-NMR、~(13)C-NMR谱确证。药动学研究表明,不同类型前药的主要药动学参数均低于原药,cLogP值在合理范围内(0~4)的原药可能不适合使用前药策略来改善其药动学行为。     

Design, synthesis, and evaluation of anti-inflammatory and ulcerogenicity of novel pyridazinone derivatives

A series of pyridazinone-containing compounds were designed and synthesized as congeners for diclofenac, the most potent and widely used NSAID. The target compounds were evaluated for their anti-inflammatory activity on rat paw edema inflammation model against diclofenac as a reference compound. Seven of the tested compounds demonstrated more than 50% inhibition of carrageenan-induced rat paw edema at a dose 10?mg/kg. The compounds, 6-(2-bromophenylamino)pyridazin-3(2H)-one 2a and 6-(2,6-dimethylphenylamino)pyridazin-3(2H)-one 2e, displayed 74 and 73.5% inflammation-inhibitory activity, respectively, which is comparable to diclofenac (78.3%) at the same dose level after 4?h. The most active compounds as anti-inflammatory agents, 2a, 2e, and 6a, displayed fewer number of ulcers and milder ulcer score than indomethacin in ulcerogenicity screening.