Management of hyperuricemia in gout: focus on febuxostat

Development and Evaluation of a Cost-Effective, Carbon-Based, Extended-Release Febuxostat Tablet

This study outlines the development of a cost-effective, extended-release febuxostat (FEB) tablet using activated charcoal as an adsorbent to enhance drug release. FEB, a BCS Class II drug, presents formulation challenges due to low solubility and high lipophilicity. We evaluated eight formulations with varying FEB-to-charcoal ratios using FTIR and DSC for physical interactions and followed USP standards for overall assessment. The optimal 1:0.25 FEB-to-charcoal ratio demonstrated a consistent 12 h zero-order release pattern. In vivo studies indicated a significantly extended plasma profile compared to immediate-release tablets. The optimal tablets demonstrated acceptable hardness and disintegration times. This innovative approach enhances patient compliance, improves bioavailability, and reduces production costs, offering a promising solution for controlled FEB delivery.

A New Avenue for Enhanced Treatment of Hyperuricemia and Oxidative Stress: Design, Synthesis and Biological Evaluation of Some Novel Mutual Prodrugs Involving Febuxostat Conjugated with Different Antioxidants

Febuxostat (FEB) is the first non-purine xanthine oxidase inhibitor (XOI) used for the treatment of hyperuricemia and gout. The oxidative stress induced by reactive oxygen species (ROS) which accompany purine metabolism by XO, could contribute to cellular damage and several pathological conditions. In this view, the present work addresses the evaluation of combining the hypouricemic effect of FEB and the free radical scavenging potential of various natural antioxidants in a single chemical entity by implementing the "mutual prodrug" strategy. Accordingly, a series of five ester prodrugs containing FEB together with different naturally occurring antioxidants namely, thioctic acid (4), thymol (5), menthol (6), vanillin (7), and guaiacol (8) was synthesized. Prominently, all the chemically conjugated prodrugs (4 - 8) revealed an obvious increase in the hypouricemic and antioxidant potentials when compared with their corresponding promoieties and physical mixtures. Moreover, they showed a potential protective effect against CCl4-induced hepatotoxicity and oxidative stress, together with no cytotoxicity on normal breast cells (MCF10A). Furthermore, the in vitro chemical and enzymatic stability studies of the prodrugs (4 - 8) using a developed HPLC method, verified their stability in different pHs, and rapid hydrolysis in rabbit plasma and liver homogenate to their parent metabolites. Moreover, the prodrugs (4 - 8) showed higher lipophilicity and lower aqueous solubility when compared to the parent drugs. Finally, the obtained merits from the implementation of the mutual prodrug strategy would encourage further application in the development of promising candidates with high therapeutic efficacy and improved safety profiles.

Quercetin-enriched Lactobacillus aviarius alleviates hyperuricemia by hydrolase-mediated degradation of purine nucleosides

The development of hyperuricemia (HUA) and gout is associated with dysbiosis of the gut microbiota. Quercetin can reduce serum uric acid levels and thus alleviate HUA by modulating the gut microbiota. However, the detailed mechanisms involved in this process are not fully understood. Here, we showed that quercetin significantly reduced the serum uric acid level in a chicken HUA model by altering the chicken cecal microbiota structure and function and increasing the abundance of Lactobacillus aviarius. An L. aviarius strain, CML180, was isolated from the quercetin-treated chicken gut microbiota. Strain characterization indicated that quercetin promoted the growth of L. aviarius CML180 and increased its adhesion, hydrophobicity, and co-aggregation abilities. Gavage of live L. aviarius CML180 to a mouse model of HUA-established by adenosine and potassium oxonate-reduced the serum uric acid level and alleviated HUA. The ability of L. aviarius CML180 to decrease the level of uric acid was due to its degradation of purine nucleosides, which are the precursors for uric acid production. A nucleoside hydrolase gene, nhy69, was identified from the genome of L. aviarius CML180, and the resulting protein, Nhy69, exhibited strong purine nucleoside-hydrolyzing activity at mesophilic temperature and neutral pH conditions. These findings provide mechanistic insights into the potential of quercetin to treat HUA or gout diseases via a specific gut microbe.

Pyrosulfite-Involved Synthesis of Sulfides by Palladium-Catalyzed Decarboxylative Couplings

The decarboxylative coupling using carboxylic acid and potassium metabisulfite, promoted by a palladium catalyst, is reported for the generation of sulfides. The coupling is performed using the easily available carboxylic acid and environmentally friendly inorganic sulfides as a divalent inorganic sulfur source. Not only aromatic acids but also aliphatic carboxylic acids are workable during the couplings. The method is applicable and practical to a scope of 20 examples and drug molecules.

Towards the Development of Dual Hypouricemic and Anti-inflammatory Candidates: Design, Synthesis, Stability Studies and Biological Evaluation of Some Mutual Ester Prodrugs of Febuxostat-NSAIDs

Treatment of gout involves two basic approaches: reducing the serum uric acid mainly by xanthine oxidase inhibitors (XOIs) and alleviating the intensity of the accompanying acute arthritic inflammation using non-steroidal anti-inflammatory drugs (NSAIDs). Febuxostat (FEB) is the first non-purine XOI approved for the treatment of hyperuricemia and gout. The present study aims at combining the hypouricemic effect of FEB and the anti-inflammatory (AI) properties of NSAIDs in a single entity by adopting the "mutual prodrug" approach. Accordingly, a series of seven ester prodrugs comprising basically FEB together with different NSAIDs namely, diclofenac (4), ibuprofen (5), ketoprofen (6), indomethacin (7), naproxen (8), ketorolac (9) and etodolac (10) was synthesized. All the investigated seven prodrugs (4-10) were equipotent or even superior to their corresponding parent drugs in the hypouricemic and AI activities, together with a gastrointestinal (GI) safety profile. Among this series, the prodrug FEB-DIC (4) showed excellent dual in vivo hypouricemic and anti-inflammatory activity (43.60 % and 15.96 %, respectively) when compared to the parent drugs FEB and diclofenac (36.82 % and 12.10 %, respectively) and its physical mixture (37.28 % and 12.41 %, respectively). Investigation of the in vitro chemical stability and hydrolysis of the prodrug (4) in aqueous and biological samples using a developed HPLC method confirmed its stability in various pHs, whereas rapid hydrolysis to the parent drugs in liver homogenate and human plasma was proven. Finally, it is concluded that the mutual prodrug approach could be successfully used in drug design and development for overcoming undesirable difficulties without losing the desired activities of the parent drugs.

Febuxostat-based amides and some derived heterocycles targeting xanthine oxidase and COX inhibition. Synthesis, in vitro and in vivo biological evaluation, molecular modeling and in silico ADMET studies

Various febuxostat derivatives comprising carboxamide functionalities and different substituted heterocycles were synthesized and evaluated for their biological activities as xanthine oxidase (XO) and cyclooxygenase (COX) inhibitors. All the tested compounds exhibited variable in vitro XO inhibitory activities (IC₅₀ values 0.009-0.077 µM), among which the analog 17 has emerged as the most potent derivative (IC₅₀ 0.009 µM), representing nearly 3-times the potency of febuxostat (IC₅₀ 0.026 µM). The same analogs were further investigated for their in vitro COX-1 and COX-2 inhibitory activity, where fifteen analogs demonstrated recognizable COX-2 inhibitory potential (IC₅₀ values range 0.04 - 0.1 µM), when correlated with celecoxib (IC₅₀ 0.05 µM), together with appreciable selectivity indices. Compounds 5a, 14b, 17, 19c, 19e and 21b that showed significant in vitro XO and/ or COX inhibitory potentials were further investigated for their in vivo hypouricemic as well as anti-inflammatory activities. Interestingly, the in vivo results were concordant with the collected in vitro data. Docking of compounds 5a, 14b, 17, 19c, 19e and 21b with the active sites of XO and COX-2 isozymes demonstrated superior binding profile compared with the reported ligands (febuxostat and celecoxib, respectively). Their docking scores were reasonable and cohering to a great extent with their corresponding in vitro IC₅₀ values. Moreover, in silico computation of the predicted pharmacokinetic and toxicity properties (ADMET), together with the ligand efficiency (LE) of the same six compounds suggesting their liability to act as new orally active drug candidates with a predicted high safety profile.

The efficacy and tolerability of febuxostat treatment in a cohort of Chinese Han population with history of gout

Objective

To measure the effect of febuxostat on the serum levels of uric acid (sUA) and the proinflammatory cytokines interleukin (IL)-6, IL-17 and tumour necrosis factor-α (TNF-α) in Chinese Han patients with gout and hyperuricaemia.

Methods

This randomized, double-blind, placebo-controlled pilot study enrolled patients with gout and hyperuricaemia (sUA ≥ 8 mg/dl). Patients were randomized to receive either febuxostat 80 mg or placebo once daily for 24 weeks. The serum levels of sUA, IL-6, IL-17 and TNF-α were measured at weeks 0 (baseline), 2, 4, 8, 12, 16 and 24. Baseline clinical and demographic characteristics were recorded for all patients.

Results

A total of 156 patients were randomized: placebo group (n = 78) and febuxostat group (n = 78). The febuxostat group showed a significantly greater reduction in sUA compared with the placebo group. Serum uric acid concentration was reduced below 8 mg/dl in 46 of 61 patients (75.4%) by week 24. There were also reductions in the serum levels IL-6, IL-17 and TNF-α in the febuxostat group. In the febuxostat group, 10 of 78 patients (12.82%) discontinued treatment due to adverse drug reactions.

Conclusion

Febuxostat reduced the levels of sUA, TNF-α, IL-6 and IL-17, but there were some side-effects.

Treatment of atypical gouty arthritis of the hip using total hip arthroplasty: A case report

RATIONALE

Gout and gouty arthritis typically involve peripheral and monoarticular joints, especially the first metatarsophalangeal joint and knees. Hip involvement in patients with gout is rare, and its diagnosis is very difficult, especially in the late stages of the disease. Total hip arthroplasty could be a surgical treatment for atypical gouty arthritis of the hip; however, few cases have been reported.

PATIENT CONCERNS

We reported an uncommon case of a 74-year-old man without typical symptoms of hip gout arthritis whom was misdiagnosed as having avascular necrosis of the femoral head.

DIAGNOSES

Clinical examination and imaging revealed bilateral avascular necrosis of the femoral head. However, the final pathology report revealed left hip gout arthritis.

INTERVENTIONS

The patient underwent left total hip arthroplasty and was followed up for 3years.

OUTCOMES

The outcome was favorable. The function of the left hip was almost normal.

LESSONS

Our case indicated the difficulty of the diagnosis of hip gout arthritis. Due to the lower rates of hip gout arthritis and lack of typical clinical examination, it is easy to misdiagnose. Furthermore, surgical treatment for the late stage of hip gout arthritis has not previously been reported. In our case, total hip arthroplasty proved to be a good option.

An Improved Method for the Synthesis of Butein Using SOCl2/EtOH as Catalyst and Deciphering Its Inhibition Mechanism on Xanthine Oxidase

Butein (3,4,2',4'-tetrahydroxychalcone) belongs to the chalcone family of flavonoids and possesses various biological activities. In this study, butein was synthesized through aldol condensation catalyzed by thionyl chloride (SOCl₂)/ethyl alcohol (EtOH) for the first time. The optimal reaction conditions including the molar ratio of reactants, the dosage of catalyst, and the reaction time on the yield of product were investigated, and the straightforward strategy assembles the yield of butein up to 88%. Butein has been found to inhibit xanthine oxidase (XO) activity. Herein, the inhibitory mechanism of butein against XO was discussed in aspects of inhibition kinetic, fluorescence titration, synchronous fluorescence spectroscopy, and molecular docking. The inhibition kinetic analysis showed that butein possessed a stronger inhibition on XO in an irreversible competitive manner with IC₅₀ value of 2.93 × 10^-6 mol L^-1. The results of fluorescence titrations and synchronous fluorescence spectroscopy indicated that butein was able to interact with XO at one binding site, and the fluorophores of XO were placed in a more hydrophobic environment with the addition of butein. Subsequently, the result of molecular docking between butein and XO protein revealed that butein formed hydrogen bonding with the amino acid residues located in the hydrophobic cavity of XO. All the results suggested that the inhibitory mechanism of butein on XO may be the insertion of butein into the active site occupying the catalytic center of XO to avoid the entrance of xanthine and inducing conformational changes in XO.

Inhibitors of Xanthine Oxidase: Scaffold Diversity and Structure-Based Drug Design

Xanthine oxidase (XO) is the enzyme responsible for the catabolism of purines and their conversion into uric acid. XO is thus the target for the treatment of hyperuricemia and gout. For more than 50 years the only XO inhibitor drug available on the market was the purine analogue allopurinol. In the last decade there has been a resurgence in the search for new inhibitors of XO, as the activity of XO and hyperuricemia have also been associated with a variety of conditions such as diabetes, hypertension, and other cardiovascular diseases. In recent years the non-purine inhibitor febuxostat was approved in Europe and the USA for the treatment of hyperuricemia. This drug was followed by another XO inhibitor called topiroxostat. This review discusses the molecular structures and activities of the multiple classes of inhibitors that have been developed since the discovery of allopurinol, with a brief review of the molecular interactions between inhibitors and XO active site residues for the most important molecules. The challenges ahead for the discovery of new inhibitors of XO with novel chemical structures are discussed.

A retrospective investigation of HLA-B*5801 in hyperuricemia patients in a Han population of China

BACKGROUND

Hyperuricemia and gout have become increasingly prevalent in China. Allopurinol is an effective urate-lowering therapy, but it has severe side effects. HLA-B*5801 is highly associated with the allopurinol-induced toxic epidermal necrolysis and Stevens-Johnson syndrome.

PATIENTS AND METHODS

In this retrospective report, we had genotyped HLA-B*5801 in 253 cases of hyperuricemia and gout patients in a Han population in Shenzhen and analyzed the clinical management of medications.

RESULTS

We found 30 carriers of the HLA-B*5801 allele in 253 cases of hyperuricemia or gout patients in the population (11.9%). Allopurinol was prescribed in both HLA-B*5801-positive and HLA-B*5801-negative groups. The evaluation of four models with or without genetic screening and management of allopurinol or febuxostat indicated that the HLA-B*5801 screening had significant cost benefit for clinical management.

CONCLUSION

For appropriate management and cost-effectiveness, the HLA-B*5801 allele should be screened in all patients with hyperuricemia and gout in the Chinese population.

A novel approach to design febuxostat-salicylic acid eutectic system: evaluation and characterization

The current study was aimed at investigating the febuxostat-salicylic acid (FXT-SAA) eutectic system using two polymorphs of FXT, form Q and form A.

Successful febuxostat desensitization in a patient with febuxostat hypersensitivity: A Malaysian experience

Over the years, allopurinol has been widely used as the preferred choice of urate lowering therapy in patients with gout. However, its role in patients with renal impairment is limited; and adverse reactions are well documented. Febuxostat, a newer oral non-purine xanthine oxidase inhibitor has been proven in several trials to be more effective and tolerable compared to allopurinol and may be used in patients with renal impairment. Here, we describe a case of successful febuxostat desensitization in a patient with a history of allopurinol- and febuxostat-induced adverse cutaneous reaction, as well as the protocol utilized.

Crystal arthritides - gout and calcium pyrophosphate arthritis : Part 3: Treatment

The treatment of gout is based on several principles. Symptom control and termination of the inflammatory process are important early goals, whereas the urate level should be lowered in the long term to prevent further gout attacks and complications. The non-pharmacological approach is based on individually informing the patient on dietary measures and changes of life style. Besides physical measures, such as cold applications on the affected joint, various medications are available for treatment of an acute gout attack. The choice of drug depends on the individual risk profile. If non-steroidal anti-inflammatory drugs (NSAID) and coxibs are chosen it should be taken into account that the use is restricted in patients with renal insufficiency. Moreover, these drugs may have gastrointestinal side effects and are associated with increased cardiovascular morbidity and mortality. Colchicine has gastrointestinal side effects at high dosages but can also be used for differential diagnostics if there is a quick response to treatment. Steroids are an effective alternative and can be given orally or parenterally in patients with dysphagia. Moreover, steroids can be used in cases of renal insufficiency. After symptoms of the acute attack have subsided, urate lowering therapy should be initiated to prevent further attacks. Low-dose urate lowering therapy can be started during an acute gout attack when acute therapy is initiated. Allopurinol is still the medication of choice but its use is restricted in patients with renal insufficiency. A rare but serious side effect is allopurinol hypersensitivity syndrome. Febuxostat can be an alternative in patients who do not tolerate allopurinol. In February 2016, lesinurad, an URAT-1 and OAT-4 inhibitor, was approved in combination with allopurinol or febuxostat. Data on the effectiveness and safety of synthetic uricases and biologicals are still sparse for elderly patients. These substances are reserved for severe cases of gout.

Crystal arthritides - gout and calcium pyrophosphate arthritis : Part 2: clinical features, diagnosis and differential diagnostics

Gout develops in four stages beginning with an asymptomatic increase in blood levels of uric acid. An acute gout attack is an expression of an underlying inflammatory process, which in the course of time is self-limiting. Without therapy monosodium urate crystals remain in the synovial fluid and synovial membrane and trigger more acute attacks. In the course of the disease monosodium urate crystals form deposits (tophi) leading in severe forms to irreversible joint deformities with loss of functionality. In 20% of cases gout leads to involvement of the kidneys. Overproduction of uric acid can cause nephrolithiasis. These stones can be composed of uric acid or calcium phosphate. Another form of kidney disease caused by gout is uric acid nephropathy. This is a form of abacterial chronic inflammatory response with deposition of sodium urate crystals in the medullary interstitium. Acute obstructive nephropathy is relatively rare and characterized by renal failure due to uric acid precipitation in the tubules because of rapid cell lysis that occurs, for example, with chemotherapy. There is a causal interdependence between the occurrence of hyperuricemia and hypertension. Uric acid activates the renin-angiotensin-aldosterone (RAA) system and inhibits nitric oxide (NO) with the possible consequence of a rise in systemic vascular resistance or arteriolar vasculopathy; however, uric acid is also an apparently independent risk factor for atherosclerosis. In contrast to young patients, the diagnosis of an acute gout attack in the elderly can be a challenge for the physician. Polyarticular manifestations and obscure symptoms can make it difficult to differentiate it from rheumatoid arthritis and calcium pyrophosphate deposition disease (CPPD). Aspiration of synovial fluid with visualization of urate crystals using compensated polarized light microscopy is the gold standard for diagnosis of acute gout. Moreover, analysis of synovial fluid enables a distinction from septic arthritis by Gram staining and bacterial culture. Soft tissue ultrasonography is useful to detect affected synovial tissue and monosodium urate crystals within the synovial fluid. Involvement of bone occurs relatively late in the disease so that x‑ray images are not useful in the early stages but might be helpful in differential diagnostics. Dual energy computed tomography (CT) and magnetic resonance imaging (MRI) can be used for certain indications.

2-Benzamido-4-methylthiazole-5-carboxylic Acid Derivatives as Potential Xanthine Oxidase Inhibitors and Free Radical Scavengers

The new chemical entities febuxostat and topiroxostat have been approved by the US Food and Drug Administration, opening new avenues for exploiting different heterocycles other than purines as xanthine oxidase (XO) inhibitors. A different series of substituted 2-benzamido-4-methylthiazole-5-carboxylic acid derivatives (5a-r) was synthesized and characterized by the collective use of IR, ¹ H and ¹³ C NMR, and mass spectroscopy, for the treatment of gout and hyperuricemia. In vitro studies of the synthesized derivatives revealed that the presence of a fluoro group at the para position in 5b (IC50 = 0.57 μm) and a chloro group in 5c (IC50 = 0.91 μm) signifies excellent XO inhibitory activity among the series, along with their DPPH free radial scavenging activity. In vivo serum uric acid inhibition studies established that 5b and 5c displayed 62 and 53% uric acid inhibition, respectively. Studies on enzyme kinetics indicated that 5b acts as a mixed type inhibitor. In silico prediction by various softwares also helped in the recognition of potent XO inhibitors.

Allopurinol and oxypurinol promote osteoblast differentiation and increase bone formation

Allopurinol and its active metabolite, oxypurinol are widely used in the treatment of gout and hyperuricemia. They inhibit xanthine oxidase (XO) an enzyme in the purine degradation pathway that converts xanthine to uric acid. This investigation examined the effect of allopurinol and oxypurinol on bone formation, cell number and viability, gene expression and enzyme activity in differentiating and mature, bone-forming osteoblasts. Although mRNA expression remained relatively constant, XO activity decreased over time with mature osteoblasts displaying reduced levels of uric acid (20% decrease). Treatment with allopurinol and oxypurinol (0.1-1 µM) reduced XO activity by up to 30%. At these concentrations, allopurinol and oxypurinol increased bone formation by osteoblasts ~4-fold and ~3-fold, respectively. Cell number and viability were unaffected. Both drugs increased tissue non-specific alkaline phosphatase (TNAP) activity up to 65%. Osteocalcin and TNAP mRNA expression was increased, 5-fold and 2-fold, respectively. Expression of NPP1, the enzyme responsible for generating the mineralisation inhibitor, pyrophosphate, was decreased 5-fold. Col1α1 mRNA expression and soluble collagen levels were unchanged. Osteoclast formation and resorptive activity were not affected by treatment with allopurinol or oxypurinol. Our data suggest that inhibition of XO activity promotes osteoblast differentiation, leading to increased bone formation in vitro.

Synthesis and bioevaluation of 2-phenyl-5-methyl-2H-1,2,3-triazole-4-carboxylic acid/carbohydrazide derivatives as potent xanthine oxidase inhibitors

A series of 2-phenyl-5-methyl-2H-1,2,3-triazole-4-carboxylic acids/carbohydrazides as analogues of febuxostat were synthesized and evaluated for their in vitro xanthine oxidase (XO) inhibitory activity.

Effect of canagliflozin on serum uric acid in patients with type 2 diabetes mellitus

Hyperuricaemia is associated with an increased risk of gout, kidney stones and cardiovascular disease. The present post hoc analysis of pooled data from four placebo-controlled phase III studies assessed the effect of canagliflozin, a sodium-glucose co-transporter 2 inhibitor, on serum uric acid levels in patients with type 2 diabetes mellitus (T2DM) and in a subset of patients with hyperuricaemia [defined as baseline serum uric acid ≥475 µmol/l (∼8 mg/dl)]. At week 26, canagliflozin 100 and 300 mg were associated with a ∼13% reduction in serum uric acid compared with placebo. In the subset of patients with hyperuricaemia, placebo-subtracted percent reductions in serum uric acid were similar to those in the overall cohort. More patients in the hyperuricaemic group achieved a serum uric acid level of <360 µmol/l (∼6 mg/dl) with both canagliflozin 100 mg (23.5%) and 300 mg (32.4%) compared with placebo (3.1%). Incidences of gout and kidney stones were low and similar across groups. In conclusion, canagliflozin treatment decreased serum uric acid in patients with T2DM, including those with baseline hyperuricaemia.

Synthesis and bioevaluation of 2-phenyl-4-methyl-1,3-selenazole-5-carboxylic acids as potent xanthine oxidase inhibitors

A series of 2-phenyl-4-methyl-1,3-selenazole-5-carboxylic acid derivatives (8a-f, 9a-m) were synthesized and evaluated for inhibitory activity against xanthine oxidase in vitro. Structure-activity relationship analyses have also been presented. Most of the target compounds exhibited potency levels in the nanomolar range. Compound 9e emerged as the most potent xanthine oxidase inhibitor (IC50 = 5.5 nM) in comparison to febuxostat (IC50 = 18.6 nM). Steady-state kinetics measurements with the bovine milk enzyme indicated a mixed type inhibition with Ki and Ki' values of 0.9 and 2.3 nM, respectively. A molecular modeling study on compounds 9e was performed to gain an insight into its binding mode with xanthine oxidase, and to provide the basis for further structure-guided design of new non-purine xanthine oxidase inhibitors related with 2-phenyl-4-methyl-1,3-selenazole-5-carboxylic acid scaffold.

Pharmacokinetics and pharmacodynamics of febuxostat under fasting conditions in healthy individuals

The aim of the present study was to investigate the pharmacokinetic and pharmacodynamic characteristics of febuxostat following the administration of single and multiple oral doses under fasting conditions to healthy individuals. Thirty-six healthy subjects were randomly divided into three groups, each containing 12 subjects (six male and six female) as follows: Group A, treated with a single oral dose of febuxostat (40 mg); group B, treated with a single oral dose of febuxostat (80 mg) followed by multiple oral doses of febuxostat for 7 days; and group C, treated with a single oral dose of febuxostat (120 mg). Blood samples were collected, and the plasma drug levels and serum uric acid (UA) concentrations were determined by clinical laboratory testing. Febuxostat displayed a linear pharmacokinetic profile for oral doses of 40 to 120 mg. Drug accumulation was not detected following multiple oral doses. When febuxostat was administered as single doses of 40, 80 and 120 mg, the 24-h UA concentration (UA24) values displayed a linear correlation with the dosage. The relationship between UA24 and the three single dose levels (40, 80 and 120 mg) was analyzed. The difference in UA24 between every single dose was significant (P<0.05). After 3 and 7 days of dosing, reductions of 46.67 and 52.69%, respectively, were observed in UA24. On day 7 of dosing, the mean reduction in the UA concentration was 51.83±7.00%. This study demonstrates that febuxostat reduces serum UA concentrations in a dose-linear manner.

Reducing effect of mangiferin on serum uric acid levels in mice

CONTEXT

Mangiferin, a natural bioactive xanthone C-glycoside, is widely present in medicinal plants like the leaf of Mangifera indica L. (Anacardiaceae). It has been reported that mangiferin possesses a variety of biological activities, including antidiabetic, hepatoprotective, anti-inflammatory, antioxidant, and anticarcinogenic.

OBJECTIVE

The hypouricemic effect and xanthine oxidoreductase (XOR) inhibitory activity of mangiferin were investigated here for the first time.

MATERIALS AND METHODS

The hypouricemic effect of mangiferin was investigated in normal and hyperuricemic mice induced by potassium oxonate. Mangiferin at a dose of 0.75-100.0 mg/kg was given intragastrically to mice. The serum urate levels were determined using the phosphotungstic acid method. The hepatic activities of xanthine dehydrogenase (XDH) and xanthine oxidase (XOD) in hyperuricemic mice were assayed using commercially available kits.

RESULTS

The results showed that mangiferin at a dose of 1.5, 3.0, and 6.0 mg/kg significantly reduced the serum urate levels (148.7 ± 37.8, 142.2 ± 44.5, 121.7 ± 21.7 µmmol/L) in hyperuricemic mice, compared with untreated hyperuricemic mice (201.8 ± 71.2 µmmol/L). However, mangiferin did not decrease the serum urate levels in normal mice until mangiferin was up to 100 mg/kg. In addition, the hepatic activities of XDH in hyperuricemic mice were significantly decreased by mangiferin, while no changes of XOD were observed. Acute toxicity study in mice showed that mangiferin was very safe at a dose of up to 25 g/kg.

DISCUSSION AND CONCLUSION

These findings demonstrate that mangiferin has the potential to be developed as a new therapeutic agent for the treatment of hyperuricemia and gout.

Synthesis, biological evaluation, and molecular docking of N-{3-[3-(9-methyl-9H-carbazol-3-yl)-acryloyl]-phenyl}-benzamide/amide derivatives as xanthine oxidase and tyrosinase inhibitors

Claisen-Schmidt condensation of 3-formyl-9-methylcarbazole with various amides of 3-aminoacetophenone afforded N-{3-[3-(9-methyl-9H-carbazol-3-yl)-acryloyl]-phenyl}-benzamide/amide derivatives. All compounds were investigated for their in vitro xanthine oxidase (XO), tyrosinase and melanin production inhibitory activity. Most of the target compounds had more potent XO inhibitory activity than the standard drug (IC(50) = 4.3-5.6 μM). Interestingly, compound 7q bearing cyclopropyl ring was found to be the most potent inhibitor of XO (IC(50) = 4.3 μM). Molecular modelling study gave an insight into its binding modes with XO. Compounds 7a, 7d, 7e, 7g, and 7k were found to be potent inhibitors of tyrosinase (IC(50) = 14.01-17.52 μM). These results suggest the possible use of these compounds for the design and development of novel XO and tyrosinase inhibitors.

Paradoxical and bidirectional drug effects

A paradoxical drug reaction constitutes an outcome that is opposite from the outcome that would be expected from the drug's known actions. There are three types: 1. A paradoxical response in a condition for which the drug is being explicitly prescribed. 2. Paradoxical precipitation of a condition for which the drug is indicated, when the drug is being used for an alternative indication. 3. Effects that are paradoxical in relation to an aspect of the pharmacology of the drug but unrelated to the usual indication. In bidirectional drug reactions, a drug may produce opposite effects, either in the same or different individuals, the effects usually being different from the expected beneficial effect. Paradoxical and bidirectional drug effects can sometimes be harnessed for benefit; some may be adverse. Such reactions arise in a wide variety of drug classes. Some are common; others are reported in single case reports. Paradoxical effects are often adverse, since they are opposite the direction of the expected effect. They may complicate the assessment of adverse drug reactions, pharmacovigilance, and clinical management. Bidirectional effects may be clinically useful or adverse. From a clinical toxicological perspective, altered pharmacokinetics or pharmacodynamics in overdose may exacerbate paradoxical and bidirectional effects. Certain antidotes have paradoxical attributes, complicating management. Apparent clinical paradoxical or bidirectional effects and reactions ensue when conflicts arise at different levels in self-regulating biological systems, as complexity increases from subcellular components, such as receptors, to cells, tissues, organs, and the whole individual. These may be incompletely understood. Mechanisms of such effects include different actions at the same receptor, owing to changes with time and downstream effects; stereochemical effects; multiple receptor targets with or without associated temporal effects; antibody-mediated reactions; three-dimensional architectural constraints; pharmacokinetic competing compartment effects; disruption and non-linear effects in oscillating systems, systemic overcompensation, and other higher-level feedback mechanisms and feedback response loops at multiple levels. Here we review and provide a compendium of multiple class effects and individual reactions, relevant mechanisms, and specific clinical toxicological considerations of antibiotics, immune modulators, antineoplastic drugs, and cardiovascular, CNS, dermal, endocrine, musculoskeletal, gastrointestinal, haematological, respiratory, and psychotropic agents.

Rhazes viewpoints about causes, diagnosis, treatment and prognosis of gout

Gout, a medical condition of acute inflammatory joint disorders, has been recognized from the antiquity. However, the name of Rhazes, a Persian historic physician who has described the etiology, signs, symptoms, epidemiology, treatment and prevention of this malady more than a thousand year ago, hasn't been taken into consideration appropriately. In this article, we studied and reported several chapters of Alhawi which is considered the most important Rhazes's medical textbook, focussing on his hypotheses because he has described this disease more manifestly. His original manuscripts are originally written in Arabic and they hadn't been translated to Persian until 1998. We intend to compare Rhazes opinions about gout with those of the literature in the area of rheumatology. According to our findings, Rhazes documented the symptoms of gout and categorized them scientifically. His insights about the treatment of gout, side effects of pharmacotherapy and management of the patients are so interesting and wonderful. Generally most of Rhazes viewpoints about gout are correct and compatible with recent findings. More investigation on Rhazes' viewpoints can guide us to propose more reliable hypothesis and schematize cost effective studies by delving into past medical records.

Efficacy and safety of febuxostat in patients with hyperuricemia and gout

The past decade has witnessed an exponential increase of novel therapeutic modalities for a variety of rheumatic disorders, including gout. During the past few years two novel therapeutic agents have been approved by the US Food and Drug Administration for the treatment of hyperuricemia in patients with gout, one of them being febuxostat, a nonpurine selective inhibitor of xanthine oxidase. Review of its pharmacokinetics and pharmacodynamics, efficacy and safety profile, and use in gout patients with comorbid conditions reveals that age and gender have no clinically significant effect and dose adjustments based on age or gender are not required. In addition, febuxostat can be used in patients with mild-to-moderate renal or hepatic involvement. Its overall efficacy and safety profile is comparable and, in certain subsets such as gout patients with mild and moderate renal insufficiency, is superior to allopurinol.

New advances in the treatment of gout: review of pegloticase

Treatment-failure gout (TFG) affects approximately 50,000 patients or about 1% of the overall population of patients with gout in the United States of America. The severity of TFG is manifested by frequent acute attacks of disabling arthritis, chronic deforming joint disease, destructive masses of urate crystals (tophi), progressive physical disability, and poor health-related quality of life. Pegloticase (Krystexxa^®; Savient Pharmaceuticals, Inc), a novel PEGylated urate oxidase (uricase) enzyme, has been resubmitted for US Food and Drug Administration approval. In a 6-month, placebo-controlled clinical trial, 8 mg of pegloticase for every 2 weeks induced a lytic decrease of serum urate (sUr) concentrations, leading to dissolution of tophi in 40% of patients at final visit. However, 58% were nonresponders to the defined target sUr of 0.36 mmol/L (80% were nonresponders during months 3 and 6), possibly due to anti-body formation. Also, 26%–31% experienced infusion reactions (IRs) and 77% suffered from gout flares. Although long-term data are awaited, an anti-inflammatory strategy, eg, based on glucocorticosteroids, is needed to prevent pegloticase antibody formation leading to IRs and diminished or shortened efficacy, and might also prevent gout flares. According to the current clinical data, pegloticase might have an important role as a (bridging) treatment in sUr-responsive patients for tophi clearance in severe chronic refractory gout.