Optimizing therapy with allopurinol: factors limiting hypouricemic efficacy

Risk factors and management of hyperuricemia after renal transplantation

Hyperuricemia (HUA) is a common complication after renal transplantation. Currently, there is no uniform consensus on factors which increase the risk for and treatment of HUA in renal transplant recipients. The purpose of this review is to summarize current and proposed risk factors and strategies to manage HUA after renal transplantation in order to assist renal function protection and prolong graft survival time.

Therapeutic approaches in the treatment of gout

Gout is a disease in which the metabolic condition hyperuricemia leads to the formation of monosodium urate crystals, which provoke acute and chronic inflammatory responses through activation of the innate immune system. Recent advances in our knowledge of gout pathogenesis have emphasized the role of the kidneys in urate handling, the evolutionary loss of uricase as a necessary precondition for hyperuricemia, and the central role of IL-1ß in the pathogenesis of gouty inflammation. These, and other advances, have shaped our current strategies for managing gout. Here, we review the most current, evidence-based gout management approaches, including treating acute flares, addressing gout through the long-term regulation of serum urate, and prophylaxis against gouty flares during urate lowering.

Therapeutic Strategies for the Treatment of Chronic Hyperuricemia: An Evidence-Based Update

This article aims to critically review the evidence on the available therapeutic strategies for the treatment of hyperuricemia. For this reason, several papers were reviewed. Xanthine oxidase inhibitors are the safest and most effective uric acid lowering drugs for the management of chronic hyperuricemia, while the efficacy of uricosuric agents is strongly modulated by pharmacogenetics. Emergent drugs (lesinurad, peglotidase) were found to be more effective for the acute management of refractory hyperuricemia, but their use is supported by a relatively small number of clinical trials so that further well-designed clinical research is needed to deepen their efficacy and safety profile.

Clinical Effects of Xanthine Oxidase Inhibitors in Hyperuricemic Patients

This review aims to critically present the available clinical evidence supporting the treatment of chronic hyperuricemia with xanthine oxidase inhibitors. For this reason, the studies published on uric acid (UA)-lowering drugs in the English language from 2000 to August 2019 have been carefully reviewed. The terms "serum uric acid," "xanthine oxidase," "allopurinol," "febuxostat," and "topiroxostat" were incorporated into an electronic search strategy, alone and in combinations, in both MEDLINE (National Library of Medicine, Bethesda, MD) and the Cochrane Register of Controlled Trials (The Cochrane Collaboration, Oxford, UK). Even if new urate-lowering drugs seem of particular efficacy for acute treatment of refractory hyperuricemia, their use is supported by relatively small clinical evidence. On the contrary, large long-term clinical trials have demonstrated that xanthine oxidase inhibitors (XOIs, namely, allopurinol and febuxostat) are effective, safe, and relatively well-tolerated in most of the patients. They have mainly been tested in the elderly, in patients affected by chronic diseases such as heart failure and cancer, and in patients taking a large number of drugs, confirming their safety profile. Recent data also show that they could exert some positive effects on vascular health, renal function, and glucose metabolism. Their cost is also low. In conclusion, XOIs remain the first choice of UA-lowering drug for chronic treatment.

Management of hyperuricemia in asymptomatic patients: A critical appraisal

While there is consensus on starting urate-lowering therapy (ULT) in cases of symptomatic hyperuricemia, the frequent condition of asymptomatic hyperuricemia (AH) remains a challenge due to differences in the findings of studies that have addressed the issue. Uric acid has anti-oxidant properties, but high levels predispose to gout and may play a role in metabolic syndrome. We systematically evaluated randomized controlled trials (RCTs) addressing ULT in patients with AH, to assess the current evidence. We found broad heterogeneity among the studies (13 RCTs), in terms of study design and population, making findings challenging to interpret and generalize; hard end-points were not assessed. Allopurinol is often prescribed for AH despite the fact that its use is not backed by conclusive evidence from prospective RCTs, nor is it recommended by the guidelines. Its potential benefits, in terms of absolute risk reduction, must be weighed against its potential for harm since it can trigger severe adverse hypersensitivity reactions, sometimes even fatal. RCTs with hard end-points are needed to assess the risk/benefit of lowering uric acid in subjects with AH, particularly as secondary prevention for cardiovascular risk and in patients with different degrees of renal disease. To date, particularly after the result from the CARES trial, preventive treatment of asymptomatic and non-severe hyperuricemia is not recommended.

Safety and tolerability of available urate-lowering drugs: a critical review

INTRODUCTION

Urate-lowering therapy (ULT) is the cornerstone of gout management, which is a widespread chronic illness characterized by hyperuricemia, arthropathy, tophus development, and urolithiasis. Since asymptomatic increased serum urate levels are associated with a higher risk of cardiovascular, renal and metabolic disorders, a larger use of ULTs in the general population is expected in the near future.

AREAS COVERED

This review will focus on the safety and tolerability profile of the available urate-lowering drugs: xanthine oxidase inhibitors (XOIs), uricosuric agents and injectable uricases.

EXPERT OPINION

Older drugs for ULT like allopurinol are well studied and extensively described from typical adverse effects (mild skin rash) to unusual fatal reactions, while febuxostat seems to be overall well tolerated. More evidence is required to define the safety profile of topiroxostat, arhalofenate, tranilast, and sulfinpyrazone. Furthermore, there are some unanswered questions about the pharmacological interactions of probenecid and the hepatotoxicity of benzbromarone. Despite a limited use in clinical practice, combination therapy with lesinurad or verinurad and XOI is not frequently accompanied by side effects. Rasburicase and pegloticase are usually well tolerated with some specific exceptions. Before prescribing UL drugs, physicians should take into account their safety profile tailoring the treatment on the patient characteristics.

Ultra-performance hydrophilic interaction liquid chromatography coupled with tandem mass spectrometry for simultaneous determination of allopurinol, oxypurinol and lesinurad in rat plasma: Application to pharmacokinetic study in rats

A fixed dose combination of lesinurad and allopurinol has been recently approved by USFDA and EMA for treatment of gout-associated hyperuricemia in patients who have not achieved target serum uric acid levels with allopurinol alone. In this study, an ultra-performance hydrophilic interaction liquid chromatography (UPHILIC) coupled with tandem mass spectrometry method was developed and validated for simultaneous determination of allopurinol, oxypurinol and lesinurad in rat plasma. Liquid liquid extraction using ethyl acetate as extracting agent was used for samples extraction procedure. Acquity UPLC HILIC column (100 mm x 2.1, 1.7μm) was used for separation of allopurinol, oxypurinol, lesinurad and internal standard (5-Florouracil). The mobile phase consisting of acetonitrile, water and formic acid (95:5:0.1, v/v/v), were eluted at 0.3 mL/min flow rate having total chromatographic run time of 3 min per sample. The analytes were detected on Acquity triple quadrupole mass spectrometer equipped with a Z-Spray electrospray ionization (ESI). The ESI source was operated in negative mode and multiple reaction monitoring was used for ion transition for all compounds. The precursor to product ion transition of m/z 134.94 > 64.07 for allopurinol, 150.89 > 41.91 for oxypurinol, 401.90 > 176.79 for lesinurad and 128.85 >41.92 for internal standard were used for identification and quantification. The calibration curves for all analytes were found to be linear with weighing factor of 1/x² using regression analysis. The developed assay was successfully applied in an oral pharmacokinetic study of allopurinol, oxypurinol and lesinurad in rats.

Allopurinol adherence among patients with gout: an Italian general practice database study

AIMS

Allopurinol is used as long-term therapy to reduce the occurrence of gout flares. This study estimated the impact of patient adherence to allopurinol on hyperuricaemia (serum uric acid levels, sUA > 6 mg/dl) and the identification of non-adherence predictors.

METHODS

The Italian Health Search-CSD Longitudinal Patient Database was accessed to identify outpatients aged ≥ 18 years with gout and prescribed with allopurinol during the years 2002-2011. Patients with a proportion of days covered ≥ 80% were considered adherent to allopurinol. Data on sUA levels over the first year of therapy were categorised in three time-windows (30-89; 90-149; 150-365 days). Logistic regressions were used to estimate the association between adherence and hyperuricaemia, as well as non-adherence predictors.

RESULTS

A total of 3727 patients were included. In the interval 0-29 days, the proportion of patients adherent to allopurinol was 45.9%, while up to 89, 149 and 365 days the percentages were 16.7%, 10.0% and 3.2%, respectively. The proportions of hyperuricaemic patients for each time-window were 43.1%, 42.4%, 32.6% and 59.0%, 64.0%, 66.4% among adherent and non-adherent patients, respectively. In the multivariable analysis, adherence was associated with a significant lower risk of hyperuricaemia. The adjusted ORs were 0.49 (95% CI: 0.33-0.73), 0.40 (95% CI: 0.24-0.67) and 0.23 (95% CI: 0.15-0.34) for the first, second and third time-window, respectively. Patients with hypertension (adjusted OR = 0.64, 95% CI: 0.42-0.99) and history of gout flares (adjusted OR = 0.55, 95% CI: 0.32-0.95) were significantly adherent to allopurinol.

CONCLUSIONS

Adherence monitoring in patients with gout is pivotal to ensure the effectiveness of therapy. To gain a better patient adherence, the communication between physicians and patients should be improved.

Molecular and cellular effects of Tamm-Horsfall protein mutations and their rescue by chemical chaperones

Correct folding of a nascent polypeptide in the lumen of the endoplasmic reticulum (ER) into a three-dimensional conformation is a crucial step in the stability, intracellular trafficking, and targeting to the final destination of a protein. By transiently and stably expressing human-relevant mutants of Tamm-Horsfall protein in polarized Madin-Darby canine kidney cells, we show here that a cysteine-altering mutation in the evolutionally conserved cysteine-rich domain had more severe defects in ER exit and surface translocation and triggered more apoptosis than a cysteine-altering mutation outside the domain. Both mutants were able to specifically bind and trap the wild-type Tamm-Horsfall protein (THP) and prevent it from exiting the ER and translocating to the cell surface. This explains at least partly why in patients with THP-associated diseases there is a marked urinary reduction of both the mutant and the wild-type THP. Exposure of mutant-expressing cells to low temperature (30 °C), osmolytes (glycerol, trimethylamine N-oxide, and dimethyl sulfoxide), and the Ca(2+)-ATP inhibitor thapsigargin only slightly relieved ER retention and increased surface targeting of the mutants. In contrast, sodium 4-phenylbutyrate and probenecid, the latter a uricosuric drug used clinically to treat gout, markedly reduced ER retention of the mutants and increased their surface translocation and secretion into the culture media. The rescue of the THP mutants was associated with the restoration of the level and subcellular localization of cytosolic chaperone HSP70. Our results reveal intricate mechanistic details that may underlie THP-associated diseases and suggest that novel therapeutics enhancing the refolding of THP mutants may be of important value in therapy.

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.

A roadmap for education to improve the quality of care in gout

PURPOSE OF REVIEW

To describe obstacles to optimum management of gout by primary care physicians and to propose educational interventions to improve care.

RECENT FINDINGS

In the past, gout education has been hampered by infrequency of continuing medical education courses, loss of excitement for a disease in which therapies have not changed (until recently), insufficient evidence-based medicine, and the lack of motivation by physicians to re-learn this disease once in active practice. We identify 10 common myths that impede appropriate treatment of gout, identify gaps in evidence-based medicine that perpetuate those myths, and propose opportunities to improve education on these myths. It is through better gout-centered education that quality of care in gout can be enhanced. Residency may be one of the key points of intervention. As more evidence-based medicine publications address the optimum management of gout, national re-education can occur. More outreach by community rheumatologists to primary care physicians through educational programs and improved referral letters can help re-educate practitioners. Lastly, an often overlooked engine to change physician practices is consumer education, but current patient education programs are lacking.

SUMMARY

Novel education interventions for physician trainees, primary care physicians, and patients are proposed to improve the care of patients with gout.

The urate-lowering efficacy and safety of febuxostat in the treatment of the hyperuricemia of gout: the CONFIRMS trial

Introduction

The purpose of this study was to compare urate-lowering (UL) efficacy and safety of daily febuxostat and allopurinol in subjects with gout and serum urate (sUA) ≥ 8.0 mg/dL in a six-month trial.

Methods

Subjects (n = 2,269) were randomized to febuxostat 40 mg or 80 mg, or allopurinol 300 mg (200 mg in moderate renal impairment). Endpoints included the proportion of all subjects with sUA <6.0 mg/dL and the proportion of subjects with mild/moderate renal impairment and sUA <6.0 mg/dL. Safety assessments included blinded adjudication of each cardiovascular (CV) adverse event (AE) and death.

Results

Comorbidities included: renal impairment (65%); obesity (64%); hyperlipidemia (42%); and hypertension (53%). In febuxostat 40 mg, febuxostat 80 mg, and allopurinol groups, primary endpoint was achieved in 45%, 67%, and 42%, respectively. Febuxostat 40 mg UL was statistically non-inferior to allopurinol, but febuxostat 80 mg was superior to both (P < 0.001). Achievement of target sUA in subjects with renal impairment was also superior with febuxostat 80 mg (72%; P < 0.001) compared with febuxostat 40 mg (50%) or allopurinol (42%), but febuxostat 40 mg showed greater efficacy than allopurinol (P = 0.021). Rates of AEs did not differ across treatment groups. Adjudicated (APTC) CV event rates were 0.0% for febuxostat 40 mg and 0.4% for both febuxostat 80 mg and allopurinol. One death occurred in each febuxostat group and three in the allopurinol group.

Conclusions

Urate-lowering efficacy of febuxostat 80 mg exceeded that of febuxostat 40 mg and allopurinol (300/200 mg), which were comparable. In subjects with mild/moderate renal impairment, both febuxostat doses were more efficacious than allopurinol and equally safe. At the doses tested, safety of febuxostat and allopurinol was comparable.

Clinical Trial Registration

NCT00430248

Management of hyperuricemia in gout: focus on febuxostat

Gout is the most common inflammatory arthritis in an elderly population, and can be diagnosed with absolute certainty by polarization microscopy. However, diagnosis may be challenging because atypical presentations are more common in the elderly. Management of hyperuricemia in the elderly with gout requires special consideration because of co-medication, contra-indications, and risk of adverse reactions. Urate-lowering agents include allopurinol and uricosuric agents. These also must be used sensibly in the elderly, especially when renal function impairment is present. However, if used at the lowest dose that maintains the serum urate level below 5.0 to 6.0 mg/dL (0.30 to 0.36 mmol/L), the excess urate in the body will eventually be eliminated, acute flares will no longer occur, and tophi will resolve. Febuxostat, a new xanthine oxidase inhibitor, is welcomed, as few alternatives for allopurinol are available. Its pharmacokinetics and pharmacodynamics are not significantly altered in patients with moderate renal function or hepatic impairment. Its antihyperuricemic efficacy at 80 to 120 mg/day is better than “standard dosage” allopurinol (300 mg/day). Long-term safety data and efficacy data on tophus diminishment and reduction of gout flares have recently become available. Febuxostat may provide an important option in patients unable to use allopurinol, or refractory to allopurinol.

Consensus guidelines for oral dosing of primarily renally cleared medications in older adults

OBJECTIVES

To establish consensus oral dosing guidelines for primarily renally cleared medications prescribed for older adults.

DESIGN

Literature search followed by a two-round modified Delphi survey.

SETTING

A nationally representative survey of experts in geriatric clinical pharmacy.

PARTICIPANTS

Eleven geriatric clinical pharmacists.

MEASUREMENTS

After a comprehensive literature search and review by an investigative group of six physicians (2 general internal medicine, 2 nephrology, 2 geriatrics), 43 dosing recommendations for 30 medications at various levels of renal function were created. The expert panel rated its agreement with each of these 43 dosing recommendations using a 5-point Likert scale (1=strongly disagree to 5=strongly agree). Recommendation-specific means and 95% confidence intervals were estimated. Consensus was defined as a lower 95% confidence limit of greater than 4.0 for the recommendation-specific mean score.

RESULTS

The response rate was 81.8% (9/11) for the first round. All respondents who completed the first round also completed the second round. The expert panel reached consensus on 26 recommendations involving 18 (60%) medications. For 10 medications (chlorpropamide, colchicine, cotrimoxazole, glyburide, meperidine, nitrofurantoin, probenecid, propoxyphene, spironolactone, and triamterene), the consensus recommendation was not to use the medication in older adults below a specified level of renal function (e.g., creatinine clearance <30 mL/min). For the remaining eight medications (acyclovir, amantadine, ciprofloxacin, gabapentin, memantine, ranitidine, rimantadine, and valacyclovir), specific recommendations for dose reduction or interval extension were made.

CONCLUSION

An expert panel of geriatric clinical pharmacists was able to reach consensus agreement on a number of oral medications that are primarily renally cleared.