Appropriate dosing regimen of allopurinol in Japanese patients1

Allopurinol-Induced Severe Cutaneous Adverse Drug Reactions: An Analysis of Spontaneous Reports in Malaysia (2000-2018)

INTRODUCTION

Allopurinol-induced severe cutaneous adverse drug reactions (SCARs) are potentially debilitating and life-threatening reactions, which can cause a financial burden to the healthcare system.

OBJECTIVES

We aimed to identify risk factors for allopurinol-induced SCARs and to assess their impact on fatality.

METHODS

Adverse drug reaction (ADR) reports with allopurinol as suspected drug were extracted from the Malaysian pharmacovigilance database from year 2000 to 2018. Multiple logistic regression analysis was used to identify significant predictors of allopurinol-induced SCARs. We further analysed the association between covariates and SCARs-related fatality in a separate model. Level of significance was set at p value < 0.05.

RESULTS

Out of 1747 allopurinol ADR reports, 612 involved SCARs (35%). The strongest predictors significantly associated with SCARs were underlying renal disease (odds ratio [OR] 2.02; 95% confidence interval [CI] 1.36, 3.00; p = 0.001), allopurinol-prescribed dose of 300 mg/day or higher (OR 1.72; 95% CI 1.38, 2.15; p < 0.001), females (OR 1.54; 95% CI 1.24, 1.93; p < 0.001), age 65 years and above (OR 1.31; 95% CI 1.04, 1.64; p = 0.020), and allopurinol-prescribed indication. SCARs cases were higher in patients who received allopurinol for unspecified hyperuricaemia (OR 1.87; 95% CI 1.29, 2.70; p = 0.001) and off-label indications (OR 3.45; 95% CI 2.20, 5.42; p < 0.001) compared to registered indications. Fatality was associated with older age and a diagnosis of Stevens-Johnson syndrome/toxic epidermal necrolysis (SJS/TEN) overlap or TEN.

CONCLUSIONS

Malaysian pharmacovigilance data show that predictors of allopurinol-induced SCARs were elderly females, patients with underlying renal disease and high allopurinol doses. These patients need close monitoring and must be educated to stop allopurinol at the first signs of rash.

Current and future therapies for gout

INTRODUCTION

Gout is a common disease responsible for recurrent flares triggered by the deposition of monosodium urate crystals secondary to longstanding hyperuricaemia. The management of gout implies both the treatment of flares and the treatment of hyperuricaemia itself. Recent improvement in the understanding of the disease led to the development of new drugs. Areas covered: This review covers data related to 'old' treatments of flares and hyperuricaemia, evidence on the recently approved drugs and emerging therapies in development. Expert opinion: Recent data provide a good grasp of the optimal use of colchicine, corticosteroids and NSAIDs for the treatment of flares. Interleukin-1 blocking therapies have an increasing role in the management of difficult-to-treat gout. Sub-optimal use of allopurinol is common and its potency to reduce serum uric acid (SUA) levels is underestimated. Febuxostat effectively reduces SUA levels. New uricosurics, notably lesinurad and arhalofenate, in combination with xanthine oxidase inhibitors, offer promising perspectives to help a greater number of patients achieve sufficient SUA reduction.

Comparison of Drug Use Between Clinical Practice and Regulatory Approval: Results in Older Japanese Patients With Rheumatoid Arthritis, Diabetes, High Blood Pressure, or Depression

BACKGROUND

In this study, differences in older patients between drug use as reported in clinical practice and in clinical trials for regulatory approval were examined.

METHODS

Electronic medical record (EMR) data such as patient background (age, sex), concomitant drugs, data on laboratory tests, and prescribed doses of drugs from outpatients with rheumatoid arthritis, diabetes, high blood pressure, or depression at Chiba University Hospital were obtained for the period from January 2003 to December 2012. These data were compared with data from relevant clinical trials for regulatory approval in order to examine differences in drug use.

RESULTS

There were 5134 eligible patients. The prescribed doses of drugs were lower than the standard approved doses for depression and rheumatoid arthritis but were generally within the approved dose range for type 2 diabetes mellitus and hypertension. When comparing the characteristics of older patients taking tacrolimus, 5.6% to 17.0% of those would not be able to participate in clinical trials because of liver or renal abnormality, and the incidence rates of some adverse drug events (ADEs) differed significantly between clinical practice and clinical trials.

CONCLUSIONS

Appropriate doses of drugs for older patients may differ from approved doses in certain diseases. Complex situations such as a lot of polypharmacy, comorbidity, and functional impairment in older patients in clinical practice make it difficult to evaluate safety based on data from clinical trials. In the future, utilization of a database created from the EMR of older patients should be considered for assessment of drug safety in older patients in clinical practice.

Comparison of topiroxostat and allopurinol in Japanese hyperuricemic patients with or without gout: a phase 3, multicentre, randomized, double-blind, double-dummy, active-controlled, parallel-group study

WHAT IS KNOWN AND OBJECTIVE

There are no clinical reports that have compared topiroxostat, a selective xanthine oxidase inhibitor, with allopurinol in serum urate-lowering efficacy. The aim of this study was to compare the efficacy and safety of topiroxostat and allopurinol in Japanese hyperuricemic patients with or without gout.

METHODS

A phase 3, multicentre, randomized, double-blind, double-dummy, active-controlled, parallel-group study conducted in Japan. Patients who had inadequate serum urate levels (a gout patient: serum urate level ≥416·4 μmol/L; an asymptomatic hyperuricemic patient with specific complications (urinary lithiasis, hypertension, hyperlipidemia and/or diabetes): serum urate level ≥475·8 μmol/L; and an asymptomatic hyperuricemic patient with no specific complications: serum urate level ≥535·3 μmol/L) were randomized to topiroxostat 120 mg/day or allopurinol 200 mg/day, with an equal allocation ratio, for 16 weeks. To prevent the onset of gouty arthritis by rapid serum urate reduction, these doses were increased in a stepwise manner. The primary efficacy endpoint was the per cent change in serum urate level from baseline to the final visit.

RESULTS AND DISCUSSION

Overall, 206 patients were randomly assigned to topiroxostat and allopurinol. Two hundred and three patients (allopurinol: n = 105, topiroxostat: n = 98) received at least one dose of the study drug and had their serum urate level assessed at least once. The baseline characteristics were comparable between groups. The mean age of patients was 53·0 ± 11·4 years and 99% of patients were male. The primary efficacy endpoint was -34·3 ± 11·1% in the allopurinol group (n = 105) and -36·3 ± 12·7% in the topiroxostat group (n = 98). Non-inferiority of the serum urate-lowering efficacy of topiroxostat to allopurinol was proved by the predefined non-inferiority margin (95% confidence interval, -5·3 to 1·3%). The overall incidences of adverse events and adverse drug reactions were similar between both groups.

WHAT IS NEW AND CONCLUSION

Topiroxostat 120 mg/day provides non-inferior serum urate reduction compared with allopurinol 200 mg/day and is well tolerated in Japanese hyperuricemic patients with or without gout.

The prescription of allopurinol in a tertiary care centre: appropriate indications and dose adjustment

Objective

To determine the appropriateness (both indications and adequate dosage regimen via creatinine clearance estimation) of allopurinol by physicians of different specialties in a tertiary care centre.

Patients and methods

In this cross sectional study computerized clinical records of 156 adult patients who were prescribed allopurinol from 12th November to 11th December, 2011 were retrieved from Al Hada Hospital Taif Saudi Arabia. Main outcome variables were approprsiate indications of allopurinol, prescribing physician’s specialty, and dosage of allopurinol. The prescribed dosages were categorized into correct and incorrect dose adjustments based on creatinine clearance estimation. The SPSS version 16 was utilized for data analyses.

Results

The mean (±SD) age was 58.15 (±14.99) years. There were 105 (67.3%) males and 51 (32.7%) females with male to female ratio being 2:1. Allopurinol was frequently prescribed by nephrologists and family physicians in this study. Out of 156 patients, 46 (29.5%) patients received allopurinol with appropriate indications. Eighty-five (54.5%) patients were received allopurinol without dose adjustment based on their creatinine clearance estimation; among them, 21 (13.5%) received allopurinol with appropriate indications.

Conclusion

The inappropriate use of allopurinol (both the indication and prescribed dosage) is still a major problem in a large tertiary care centre. Furthermore, the specialty of physicians is also a contributory factor in this inappropriateness.

An allopurinol-controlled, multicenter, randomized, open-label, parallel between-group, comparative study of febuxostat (TMX-67), a non-purine-selective inhibitor of xanthine oxidase, in patients with hyperuricemia including those with gout in Japan: phase 2 exploratory clinical study

BACKGROUND

Allopurinol has been widely used for the treatment of hyperuricemia, however, it may be associated with various adverse effects. Febuxostat has been identified as a potentially safe and efficacious alternative.

OBJECTIVES

Febuxostat was administered to patients with hyperuricemia including gout in Japan to compare its efficacy and safety with those of allopurinol.

METHODS

The starting dose of febuxostat and allopurinol was 10 and 100 mg/d, respectively, and was increased to the fixed maintenance dose of 40 or 60 mg/d for febuxostat and 300 mg/d for allopurinol for 16 weeks.

RESULTS

: The percent change in the serum uric acid level at 16 weeks compared with the baseline serum uric acid level was -42.96% ± 13.33% and -52.47% ± 9.79% for the febuxostat 40- and 60-mg/d groups, respectively, and -36.55% ± 18.59% for the allopurinol group, indicating that the hypouricemic effects of febuxostat increased in a dose-dependent manner and equaled to or surpassed those of allopurinol (P = 0.0239, 2-sample t test). The percentage of patients with serum uric acid levels of 6.0 mg/dL or less at 16 weeks was 88.9% and 100% for the febuxostat 40- and 60-mg/d groups, respectively, and 68.8% for the allopurinol group, showing higher achievements for the febuxostat groups compared with the allopurinol group. All adverse drug reactions were mild to moderate in severity, and there were no severe symptoms or reactions leading to drug discontinuation.

CONCLUSIONS

These results suggest that febuxostat is safe at doses of 40 and 60 mg/d and has equal or greater efficacy than 300 mg/d allopurinol.

Xanthine oxidoreductase is involved in macrophage foam cell formation and atherosclerosis development

OBJECTIVE

Hyperuricemia is common in patients with metabolic syndrome. We investigated the role of xanthine oxidoreductase (XOR) in atherosclerosis development, and the effects of the XOR inhibitor allopurinol on this process.

METHODS AND RESULTS

Oral administration of allopurinol to ApoE knockout mice markedly ameliorated lipid accumulation and calcification in the aorta and aortic root. In addition, allopurinol treatment or siRNA-mediated gene knockdown of XOR suppressed transformation of J774.1 murine macrophage cells, treated with acetylated LDL or very low density lipoprotein (VLDL) into foam cells. This inhibitory effect of allopurinol was also observed in primary cultured human macrophages. In contrast, overexpression of XOR promoted transformation of J774.1 cells into foam cells. Interestingly, SR-A1, SR-B1, SR-B II, and VLDL receptors in J774.1 cells were reduced by XOR knockdown, and increased by XOR overexpression. Conversely, expressions of ABCA1 and ABCG1 were increased by XOR knockdown and suppressed by XOR overexpression. Finally, productions of inflammatory cytokines accompanied by foam cell formation were also reduced by allopurinol administration.

CONCLUSIONS

These results strongly suggest XOR activity and/or its expression level to contribute to macrophage foam cell formation. Thus, XOR inhibitors may be useful for preventing atherosclerosis.

Chronic kidney disease in gout in a managed care setting

Background

To study the prevalence of chronic kidney disease (CKD) and its impact on allopurinol dosing and uric acid control among patients with gout.

Methods

This was a retrospective study using data from a large US health plan. Claims and laboratory data were analyzed for enrollees from the health plan database from January 2002 through December 2005. Patients with gout were identified from pharmacy and medical claims data based on the presence of codes for gout medication or gout diagnosis. Severity of CKD was determined using the estimated glomerular filtration rate (eGFR). Allopurinol titration was defined as a change in average daily dose from first prescription to last prescription of ≥ 50 mg.

Results

A total of 3,929 patients were identified for inclusion in this study, 39% of whom had CKD (based on having an eGFR < 90 mL/min/1.73 m²). Subjects with CKD were older (p < 0.01) and more likely to be women (p < 0.01), had a greater number of comorbid conditions (p < 0.01), and were more likely to be prescribed allopurinol (p < 0.01) compared to those with no CKD. The average starting dose of allopurinol was lower among those with CKD, and it decreased with worsening kidney function. Among the 3,122 gout patients who used allopurinol, only 25.6% without CKD and 22.2% with CKD achieved a serum uric acid concentration of < 6.0 mg/dL (p = 0.0409). Also, only 15% of allopurinol users had an upward dose titration (by ≥50 mg), but the average increase in dose did not differ significantly between those with and without CKD.

Conclusions

About two out of every five patients with gout in this population had CKD. Allopurinol doses were not adjusted in the majority of CKD patients. Serum uric acid control in gout was poor among patients without CKD and even worse among those with CKD.

Optimizing therapy with allopurinol: factors limiting hypouricemic efficacy

The aim of this review is to examine clinical aspects of the use of the hypouricemic drug allopurinol. Allopurinol is a moderately active hypouricemic drug. Its activity is largely the result of the inhibition of xanthine oxidoreductase by oxypurinol, the active metabolite of allopurinol. The activity of allopurinol may be limited by oxypurinol, reducing the renal clearance of urate. Optimal use of allopurinol involves individualization of dose to attain a sufficient decrease in plasma urate concentrations. This may require a dose greater than recommended based on creatinine clearance. The initial use of an anti-inflammatory drug or low-dose colchicine decreases but does not eliminate the development of acute attacks of gout during the initiation of therapy with allopurinol. Monitoring of oxypurinol concentrations has shed some light on the efficacy of allopurinol but more data are required particularly in patients with renal impairment. Probenecid increases the hypouricemic effect of allopurinol but the favorable interaction may be significant only in patients with glomerular filtration rates greater than about 50 mL/min.

A simple method for quantification of allopurinol and oxipurinol in human serum by high-performance liquid chromatography with UV-detection

OBJECTIVES

Allopurinol is a uric acid lowering drug used in the treatment of gout and the prevention of tumor lysis syndrome. Allopurinol and its active metabolite oxipurinol inhibit xanthine oxidase, which forms uric acid from xanthine and hypoxanthine. Therapeutic drug monitoring is an important option for evaluation and optimization of allopurinol treatment in case of renal impairment, interaction with uricosuric drugs or to verify patient adherence. In this study we developed and validated a simple quantitative assay using reverse phased high-performance liquid chromatography (HPLC) with UV-detection as a method for quantification of allopurinol and oxipurinol in human serum in the presence of different frequently used drugs.

METHODS

The HPLC-UV method uses a mobile phase consisting of sodium acetate (0.02 M; pH 4.5), at a flow rate of 1.0 mL/min. Allopurinol and oxipurinol are detected by UV-absorption at 254 nm with a retention time of 9.9 min for oxipurinol and 12.3 min for allopurinol. Aciclovir is used as internal standard.

RESULTS

Validation showed for allopurinol lower and upper limits of quantification of 0.5 and 10mg/L and for oxipurinol 1 and 40 mg/L, respectively. The assay was linear over the concentration range of 0.5-10mg/L (allopurinol) and 1-40 mg/L (oxipurinol). Intra- and inter-day precision showed coefficients of variation <15% over the complete concentration range; accuracy was within 5% for allopurinol and oxipurinol. Endogenous purine-like compounds were separated from allopurinol, oxipurinol and aciclovir with a resolution factor >1.5. Exogenous purine-like compounds and co-medication frequently used by gout patients did not hinder the analysis due to the dichloromethane washing step or to low UV-absorpion at 253 nm. Serum levels of 66 patients prescribed allopurinol 300 mg/day were determined using this HPLC-UV method. Measured serum allopurinol and oxipurinol concentrations in clinical practice showed large variability with a range of <0.5-4.3 mg/L for allopurinol and <1.0-39.2 mg/L for oxipurinol, respectively.

CONCLUSION

We developed an easy-to-operate and validated HPLC-UV method for the quantification of allopurinol and oxipurinol in human serum. This method was proven to be valid for samples of gout patients frequently using concomitant medications.

Molecular analysis of thiopurine S-methyltransferase alleles in Taiwan aborigines and Taiwanese

BACKGROUND

Thiopurine S-methyltransferase (TPMT) is a cytosolic enzyme involved in the metabolism of these thiopurine drugs. Methylation of thiopurine drugs by TPMT competes with the formation of their active 6-thioguanine nucleotide metabolite, thereby potentially modulating the therapeutic and toxic effects of these drugs.

OBJECTIVE

To analyze the thiopurine S-methyltransferase allelic frequencies in Taiwan aborigines and Taiwanese.

METHODS

We used polymerase chain reaction-restriction fragment length polymorphism method to determine the allelic frequencies of TPMT variants (TPMT*1-TPMT*8) in 409 Taiwan aborigines and 117 Taiwanese.

RESULTS AND DISCUSSION

The results showed that the allelic frequencies of TPMT*1 were 99.88% and 98.72% for Taiwan aborigines and Taiwanese respectively. The allelic frequencies of TPMT*3C were 0.12% and 1.28% for Taiwan aborigines and Taiwanese respectively. No TPMT*2, 3A, 3B, 3D and 4-8 were found in these populations.

CONCLUSION

Our results provide useful information for using thiopurine drugs in these populations.

Pathophysiology, Clinical Presentation and Treatment of Gout

Gout is a common form of inflammatory arthritis that has been managed primarily in general medical practices for centuries. It appears that there has been an increasing prevalence of gout over the past decades, implying a growing public health burden. Accurate diagnosis and recognition of the various stages and manifestations of gout enable realistic goal setting for management. Recent evidence suggests new risk factors and potentially refutes others. Management of gout requires characterising and modifying risk factors and associated disorders, and commonly initiating drug therapy. Pharmacotherapy of gout includes the management of acute flares with anti-inflammatory agents such as NSAIDs and glucocorticoids and long-term treatment with urate-lowering drugs. Although pharmacotherapy is generally safe and effective, there are caveats and limitations to all gout therapies. Patient non-adherence and errors with the use of drugs for gout treatment are important factors leading to medical failures. With early intervention, careful monitoring and patient education, gout is a condition that can be managed very effectively. The advent of new drugs (such as febuxostat and urate oxidase [uricase]) and enhanced understanding of the pathogenesis of gout continue to improve our therapeutic options, particularly in a subset of patients with refractory disease and those who are intolerant to currently available medications.