Persistence with urate-lowering therapy in Australia: A longitudinal analysis of allopurinol prescriptions.

AIM: Gout is the most common form of inflammatory arthritis in men. Despite the availability of effective urate-lowering therapies (ULT), the management of gout is suboptimal due to poor persistence with ULT. This study examined national prescribing patterns of ULT to determine persistence with allopurinol in Australia. METHODS: A 10% sample of the Australian Pharmaceutical Benefits Scheme dispensing claims database was used to identify individuals initiated on allopurinol between April 2014 and December 2019. The number of allopurinol scripts dispensed was used to estimate persistence with allopurinol. Persistence was defined as the number of months from initiation until discontinuation (last prescription with no further scripts acquired for a period thereafter). Kaplan-Meier curves were used to examine persistence, while Cox regression analysis was used to examine the influence of gender, concomitant colchicine and age. RESULTS: The largest drop in persistence occurred immediately after initiation, with 34% of patients discontinuing allopurinol 300-mg therapy in the first month. Median persistence with allopurinol 300 mg was 5 months (95% confidence interval 4.76-5.24), with around 63% of individuals not persisting with this therapy for more than 12 months. Concomitant prescription of colchicine on the day of allopurinol initiation only occurred in 7% of allopurinol initiations. No increase in persistence was observed for those co-prescribed colchicine. CONCLUSION: Persistence with allopurinol was poor. More effective methods targeting prescribers, patients and systems are required to promote persistence with allopurinol. Improving persistence to allopurinol is an important public health goal given the proven potential of this medication to eliminate gout.

Expanding the role of Australian community dietitians in gout management.

AIM: Gout is a common form of inflammatory arthritis with suboptimal management. Management guidelines for gout highlight the importance of both pharmacological and non-pharmacological treatments. Dietitians can potentially assist in improving gout's associated dietary and lifestyle factors, and thereby play a role in improving its management. The aim of this study was to investigate perspectives of Australian community dietitians on whether their role in gout management could be expanded to improve management and treatment of gout. METHOD: A snowballing recruitment strategy was used. Dietitians known to the research team were invited to participate and then they suggested further dietitians. Semi-structured interviews (one-on-one) were conducted with 16 dietitians. The focus was on their experiences of contributing to the management of gout, including any barriers and facilitators experienced. Interviews were transcribed verbatim and independently analyzed by 2 reviewers to identify themes. RESULTS: The main reported role of dietitians in gout management was providing patient education. An identified facilitator was dietitians' understanding of gout and its dietary management. Barriers included the emphasis placed on medications for treatment by clinicians and patients, consultation costs, limitations in the evidence for the efficacy of dietary changes and lack of specific training in gout for dietitians. Dietitians predominantly managed the other metabolic conditions commonly associated with gout. CONCLUSION: Currently, the role dietitians play in gout management is limited. However, dietitians have the potential to take on larger roles in gout education and can also indirectly contribute by way of management of commonly associated comorbidities in gout patients.

Predicting Response or Non-response to Urate-Lowering Therapy in Patients with Gout.

PURPOSE OF REVIEW: To review the extent of treatment success or failure with the xanthine oxidoreductase inhibitors allopurinol and febuxostat and indicate how the dosage of urate-lowering therapy (ULT) may be modified to increase the response in the majority of patients with gout. RECENT FINDINGS: Gout flares are associated with serum concentrations of urate above 0.42 mmol/L (7 mg/dL). Achieving and maintaining serum urate below 0.36 mmol/L is considered an effective response to ULT. On an intention to treat basis, clinical trials indicate that allopurinol at daily doses of 100 to 300 mg decreases serum urate adequately in only about 40% of gout patients while febuxostat 80 mg daily reduces serum urate adequately in approximately 70% of gout patients. Higher doses of ULT may be required in patients receiving concomitant diuretics. The addition of a uricosuric agent to allopurinol and febuxostat therapy significantly increases the proportion of patients achieving adequate lowering of serum urate. Finally, carriers of a genetic variant of the transporter, ABCG2 (BCRP), have a decreased response to allopurinol. Careful examination of medication adherence, titration of doses, and the addition of uricosuric agents increase the percentage of patients responding to allopurinol and febuxostat.

Exploring current and potential roles of Australian community pharmacists in gout management: a qualitative study.

BACKGROUND: Gout is an increasingly prevalent form of inflammatory arthritis. Although effective treatments for gout exist, current management is suboptimal due to low medication adherence rates and treatments that are non-concordant with guidelines. Medications are the mainstay and most effective form of gout management. Thus, there is potential for community pharmacists to play an important primary health care role in gout management, however their current role and their potential to improve management of gout treatment is currently unclear. The purpose of the study is to explore the views of Australian pharmacists on their roles in gout management and to identify factors influencing their involvement in gout management. METHODS: A convenience sample of community pharmacists were invited to participate using a snowballing recruitment strategy. Semi-structured, face-to-face interviews were conducted with 15 pharmacists of varying age, gender and pharmacy experience. Interviews focused on pharmacists' experiences of managing gout, interactions with people living with gout and their perceived roles and responsibilities in gout management. Interviews were transcribed verbatim and independently analysed by two reviewers to identify themes. RESULTS: The main role of pharmacists reported in gout management was providing patient education. The greatest facilitator to pharmacists involvement in gout management was identified to be pharmacists' good understanding of gout and its management. Barriers to pharmacists involvement were identified to be difficulties in monitoring adherence to gout medications, low priority given to gout in the pharmacy compared to other chronic health conditions, and lack of specific training and/or continuing education in gout prevention and management. CONCLUSIONS: Pharmacists can expand their primary health care role in gout management, particularly in the area of ongoing provision of education to people living with gout and in monitoring medication adherence in patients. However, a number of barriers need to be overcome including difficulties in monitoring patient adherence to medications, ensuring a higher priority is given to chronic gout management and providing continuing training to community pharmacists about gout. Implications for pharmacist practice include initiating conversations about medication adherence and education when dispensing medications and undertaking continuing education in gout.

Individualising the dose of allopurinol in patients with gout.

AIMS: The aims of the study were to: 1) determine if a plasma oxypurinol concentration-response relationship or an allopurinol dose-response relationship best predicts the dose requirements of allopurinol in the treatment of gout; and 2) to construct a nomogram for calculating the optimum maintenance dose of allopurinol to achieve target serum urate (SU) concentrations. METHODS: A nonlinear regression analysis was used to examine the plasma oxypurinol concentration- and allopurinol dose-response relationships with serum urate. In 81 patients (205 samples), creatinine clearance (CLCR ), concomitant diuretic use and SU concentrations before (UP ) and during (UT ) treatment were monitored across a range of allopurinol doses (D, 50-700 mg daily). Plasma concentrations of oxypurinol (C) were measured in 47 patients (98 samples). Models (n = 47 patients) and predictions from each relationship were compared using F-tests, r2 values and paired t-tests. The best model was used to construct a nomogram. RESULTS: The final plasma oxypurinol concentration-response relationship (UT = UP - C*(UP - UR )/(ID50 + C), r2  = 0.64) and allopurinol dose-response relationship (UT = UP - D* (UP - UR )/(ID50 + D), r2  = 0.60) did not include CLCR or diuretic use as covariates. There was no difference (P = 0.87) between the predicted SU concentrations derived from the oxypurinol concentration- and allopurinol dose-response relationships. The nomogram constructed using the allopurinol dose-response relationship for all recruited patients (n = 81 patients) required pretreatment SU as the predictor of allopurinol maintenance dose. CONCLUSIONS: Plasma oxypurinol concentrations, CLCR and diuretic status are not required to predict the maintenance dose of allopurinol. Using the nomogram, the maintenance dose of allopurinol estimated to reach target concentrations can be predicted from UP .

Allopurinol: insights from studies of dose-response relationships.

INTRODUCTION: Gout is the most common inflammatory arthritis in men and is increasingly prevalent. Allopurinol is very effective at reducing plasma urate concentrations to a level sufficient to dissolve monosodium urate crystals. However, many patients fail to achieve a sufficient therapeutic response to allopurinol. Areas covered: This review covers the metabolism and pharmacokinetics of allopurinol and its active metabolite, oxypurinol and how these factors affect the plasma concentrations of urate at initiation and during long-term therapy with allopurinol. Significant aspects discussed are the importance of adherence to allopurinol therapy, allopurinol hypersensitivity reactions and insights into hyperuricemia. Expert opinion: The initial dosage of allopurinol should be low, particularly in patients with renal impairment. The dose should then be increased slowly until plasma concentrations of urate are sufficient to dissolve monosodium urate crystals (≤ 0.36 mmol/L). For this target, the maintenance dose of allopurinol can be estimated from the equation: Dose = 1413*(Up-0.36) where Up is the pre-treatment concentration of urate. Poor adherence is a major factor limiting successful therapy with allopurinol; however, its use can be improved considerably by education of patients and clinicians. Allopurinol is generally well tolerated and screening for genetic factors predictive of allopurinol hypersensitivity reactions can now be undertaken.

Xanthine oxidoreductase and its inhibitors: relevance for gout.

Xanthine oxidoreductase (XOR) is the rate-limiting enzyme in purine catabolism and converts hypoxanthine to xanthine, and xanthine into uric acid. When concentrations of uric acid exceed its biochemical saturation point, crystals of uric acid, in the form of monosodium urate, emerge and can predispose an individual to gout, the commonest form of inflammatory arthritis in men aged over 40 years. XOR inhibitors are primarily used in the treatment of gout, reducing the formation of uric acid and thereby, preventing the formation of monosodium urate crystals. Allopurinol is established as first-line therapy for gout; a newer alternative, febuxostat, is used in patients unable to tolerate allopurinol. This review provides an overview of gout, a detailed analysis of the structure and function of XOR, discussion on the pharmacokinetics and pharmacodynamics of XOR inhibitors-allopurinol and febuxostat, and the relevance of XOR in common comorbidities of gout.

Mobile applications to enhance self-management of gout.

BACKGROUND: Gout is an arthritic condition that is characterised by extremely painful, debilitating acute attacks and eventual joint and organ damage if not controlled. Despite the availability of very effective therapies that, if adhered to, will prevent acute attacks and long-term damage, the disorder is increasingly prevalent. There is an urgent need to improve self-management of gout. OBJECTIVES: Mobile health (mHealth) applications ('apps'), designed to facilitate management of chronic conditions, present novel opportunities for supporting patient self-management of gout. The aim of this review was to assess features of available gout management apps designed to assist consumers in managing their gout and their consistency with guidelines for gout management. METHODS: English-language, smart-device apps designed to assist self-management of gout were identified using search term "gout" and downloaded from Apple and Google Play app stores. To be included in the review, apps had to allow users to monitor their gout disease (e.g. serum uric acid (sUA) tracking, record acute attacks) and/or educate patients about gout. Investigators derived patient-focused recommendations for gout management from contemporary guidelines. Features of reviewed apps were independently assessed by two reviewers for their facilitation of these recommendations. RESULTS: The search identified 57 apps possibly relevant to gout management, of which six met the inclusion criteria. One app incorporated all recommendations for patient-focused gout management from guidelines including monitoring sUA, recording attacks and lifestyle advice. However, the majority of these elements were not functional within the app, and instead required users to manually complete printouts. CONCLUSIONS: Currently, only one app exists that includes all recommendations to facilitate patient self-management of gout, however some features can only be actioned manually. Given the lack of progress in achieving better patient outcomes and the promise of mHealth interventions to deliver significant gains, new or updated gout management apps are required to promote successful self-management of this chronic disease.

Hyperuricaemia: contributions of urate transporter ABCG2 and the fractional renal clearance of urate.

OBJECTIVE: To investigate the contributions towards hyperuricaemia of known risk factors, focusing on fractional (renal) clearance of urate (FCU) and variation in the ATP-binding cassette transporter, sub-family G 2 (ABCG2) gene. METHODS: The contributions of age, sex, ancestry, Q141K genotype for ABCG2, FCU, sugar-sweetened beverage and alcohol consumption, metabolic syndrome disorders and measures of renal function to the risk of hyperuricaemia were evaluated by comparing hyperuricaemic (serum urate≥0.42 mmol/L, n=448) with normouricaemic (serum urate<0.42 mmol/L, n=344) participants using stepwise logistic regression. Model performance was evaluated using the area under the receiver operator characteristic curve (AUROC). RESULTS: ABCG2 genotype, FCU, male sex, body mass index, serum triglyceride concentrations, estimated glomerular filtration rate and consumption of alcohol were the best predictors of hyperuricaemia (AUROC 0.90, 81% accuracy). Homozygosity in the 141K variant for ABCG2 conferred an adjusted OR of 10.5 for hyperuricaemia (95% CI 2.4 to 46.2). For each 1% decrease of FCU, the adjusted OR increased by 51% (OR 1.51, 95% CI 1.37 to 1.66). There was no association between ABCG2 genotype and FCU (r=0.02, p=0.83). CONCLUSIONS: The ABCG2 141K variant and the FCU contribute strongly but independently to hyperuricaemia. These findings provide further evidence for a significant contribution of ABCG2 to extra-renal (gut) clearance of urate.

The Toll-Like Receptor 4 (TLR4) Variant rs2149356 and Risk of Gout in European and Polynesian Sample Sets.

Deposition of crystallized monosodium urate (MSU) in joints as a result of hyperuricemia is a central risk factor for gout. However other factors must exist that control the progression from hyperuricaemia to gout. A previous genetic association study has implicated the toll-like receptor 4 (TLR4) which activates the NLRP3 inflammasome via the nuclear factor-κB signaling pathway upon stimulation by MSU crystals. The T-allele of single nucleotide polymorphism rs2149356 in TLR4 is a risk factor associated with gout in a Chinese study. Our aim was to replicate this observation in participants of European and New Zealand Polynesian (Maori and Pacific) ancestry. A total of 2250 clinically-ascertained prevalent gout cases and 13925 controls were used. Non-clinically-ascertained incident gout cases and controls from the Health Professional Follow-up (HPFS) and Nurses Health Studies (NHS) were also used. Genotypes were derived from genome-wide genotype data or directly obtained using Taqman. Logistic regression analysis was done including age, sex, diuretic exposure and ancestry as covariates as appropriate. The T-allele increased the risk of gout in the clinically-ascertained European samples (OR = 1.12, P = 0.012) and decreased the risk of gout in Polynesians (OR = 0.80, P = 0.011). There was no evidence for association in the HPFS or NHS sample sets. In conclusion TLR4 SNP rs2143956 associates with gout risk in prevalent clinically-ascertained gout in Europeans, in a direction consistent with previously published results in Han Chinese. However, with an opposite direction of association in Polynesians and no evidence for association in a non-clinically-ascertained incident gout cohort this variant should be analysed in other international gout genetic data sets to determine if there is genuine evidence for association.

Barriers to Care in Gout: From Prescriber to Patient.

OBJECTIVE: To explore the understanding of gout and its management by patients and general practitioners (GP), and to identify barriers to optimal gout care. METHODS: Semistructured interviews were conducted with 15 GP and 22 patients in Sydney, Australia. Discussions were focused on medication adherence, experiences with gout, and education and perceptions around interventions for gout. Interviews were audio recorded, transcribed verbatim, and analyzed for themes using an analytical framework. RESULTS: Adherence to urate-lowering medications was identified as problematic by GP, but less so by patients with gout. However, patients had little appreciation of the risk of acute attacks related to variable adherence. Patients felt stigmatized that their gout diagnosis was predominantly related to perceptions that alcohol and dietary excess were causal. Patients felt they did not have enough education about gout and how to manage it. A manifestation of this was that uric acid concentrations were infrequently measured. GP were concerned that they did not know enough about managing gout and most were not familiar with current guidelines for management. For example and importantly, the strategies for reducing the risk of acute attacks when commencing urate-lowering therapy (ULT) were not well appreciated by GP or patients. CONCLUSION: Patients and GP wished to know more about gout and its management. Greater success in establishing and maintaining ULT will require further and better education to substantially benefit patients. Also, given the prevalence, and personal and societal significance of gout, innovative approaches to transforming the management of this eminently treatable disease are needed.

Multiplicative interaction of functional inflammasome genetic variants in determining the risk of gout.

INTRODUCTION: The acute gout flare results from a localised self-limiting innate immune response to monosodium urate (MSU) crystals deposited in joints in hyperuricaemic individuals. Activation of the caspase recruitment domain-containing protein 8 (CARD8) NOD-like receptor pyrin-containing 3 (NLRP3) inflammasome by MSU crystals and production of mature interleukin-1ß (IL-1ß) is central to acute gouty arthritis. However very little is known about genetic control of the innate immune response involved in acute gouty arthritis. Therefore our aim was to test functional single nucleotide polymorphism (SNP) variants in the toll-like receptor (TLR)-inflammasome-IL-1ß axis for association with gout. METHODS: 1,494 gout cases of European and 863 gout cases of New Zealand (NZ) Polynesian (Maori and Pacific Island) ancestry were included. Gout was diagnosed by the 1977 ARA gout classification criteria. There were 1,030 Polynesian controls and 10,942 European controls including from the publicly-available Atherosclerosis Risk in Communities (ARIC) and Framingham Heart (FHS) studies. The ten SNPs were either genotyped by Sequenom MassArray or by Affymetrix SNP array or imputed in the ARIC and FHS datasets. Allelic association was done by logistic regression adjusting by age and sex with European and Polynesian data combined by meta-analysis. Sample sets were pooled for multiplicative interaction analysis, which was also adjusted by sample set. RESULTS: Eleven SNPs were tested in the TLR2, CD14, IL1B, CARD8, NLRP3, MYD88, P2RX7, DAPK1 and TNXIP genes. Nominally significant (P < 0.05) associations with gout were detected at CARD8 rs2043211 (OR = 1.12, P = 0.007), IL1B rs1143623 (OR = 1.10, P = 0.020) and CD14 rs2569190 (OR = 1.08; P = 0.036). There was significant multiplicative interaction between CARD8 and IL1B (P = 0.005), with the IL1B risk genotype amplifying the risk effect of CARD8. CONCLUSION: There is evidence for association of gout with functional variants in CARD8, IL1B and CD14. The gout-associated allele of IL1B increases expression of IL-1ß - the multiplicative interaction with CARD8 would be consistent with a synergy of greater inflammasome activity (resulting from reduced CARD8) combined with higher levels of pre-IL-1ß expression leading to increased production of mature IL-1ß in gout.

An audit of a therapeutic drug monitoring service for allopurinol therapy.

BACKGROUND: Oxypurinol, the active metabolite of allopurinol, is the major determinant of the hypouricemic effect of allopurinol. Monitoring oxypurinol concentrations is undertaken to determine adherence to therapy, to investigate reasons for continuing attacks of acute gout and/or insufficiently low plasma urate concentrations despite allopurinol treatment, and to assess the risk of allopurinol hypersensitivity, an adverse effect that has been putatively associated with elevated plasma oxypurinol concentrations. METHODS: An audit of request forms requesting plasma oxypurinol concentration measurements received by the pathology service (SydPath) at St Vincent's Hospital, Darlinghurst, Sydney was undertaken for the 7-year period January 2005-December 2011. Patient demographics, biochemical data, including plasma creatinine and uric acid concentrations, comorbidities, and concomitant medications were recorded. RESULTS: There were 412 requests for determination of an oxypurinol concentration. On 48% of occasions, the time of allopurinol dosing was recorded, while just 79 (19%) blood samples were collected 6-9 hours postdosing, the time window used to establish the therapeutic range for oxypurinol. For these optimally interpretable concentrations, 32 (8%) were within the putative therapeutic range (5-15 mg/L), while 5 (1%) were below and 41 (10%) above this range. The daily dose of allopurinol was documented on only one-third of the request forms. Individually, plasma urate and creatinine concentrations were requested concomitantly with plasma oxypurinol concentrations in 66% and 58% of the cases, respectively; while plasma oxypurinol, urate, and creatinine concentrations were requested concomitantly in 49% of the cases. CONCLUSIONS: Requesting clinicians and blood specimen collectors often fail to provide relevant information (dose, times of last dose, and blood sample collection) to allow the most useful interpretation of oxypurinol concentrations. Concomitant plasma urate and creatinine concentrations should be requested to allow more complete interpretation of the data.

Allopurinol hypersensitivity: a systematic review of all published cases, 1950-2012.

BACKGROUND: Allopurinol is the primary therapy for the management of chronic gout. Utilization of allopurinol has increased in tandem with the growing prevalence of gout globally. This exposes more patients to the risk of allopurinol hypersensitivity (AH), a rare adverse reaction characterised by a spectrum of cutaneous reactions and systemic manifestations. Severe forms of AH have been associated with high mortality. The pathophysiology underlying this reaction remains unknown, but several risk factors have been proposed. OBJECTIVE: The aim of this study was to review all published cases of AH documented in the literature in order to better understand the constellation of factors predisposing to this reaction, building on previous reviews by Lupton and Odom, Singer and Wallace and Arellano and Sacristan. METHODS: A literature search was conducted in MEDLINE and EMBASE to identify relevant articles published between January 1950 and December 2012, with no language restrictions imposed. Articles that were included reported either allopurinol-induced cutaneous manifestations alone or satisfied the diagnostic criteria for AH as defined by Singer and Wallace. RESULTS: Nine hundred and one patients (overall AH cohort) were identified from 320 publications. Of these patients, 802 satisfied the Singer and Wallace criteria ('Singer and Wallace' cohort) while 99 patients had only mild cutaneous manifestations ('non-Singer and Wallace' cohort). Data were often incomplete; hence the results reported reflect the fractions of the subsets of the cohort where the data in question were available. In the overall AH cohort, 58 % (416/722) were male. The majority (73 %; 430/590) of patients were Asian. Renal impairment (48 %; 182/376) and hypertension (42 %; 160/376) were the most common chronic conditions; accordingly, diuretics (45 %; 114/252) and antihypertensives (39 %; 99/252) were the most prevalent concomitant medications. Allopurinol was prescribed for approved indications (chronic gout and chemoprophylaxis) in only 40 % (186/464) of patients. The median allopurinol dose was 300 mg/day (range 10-1,000 mg/day) and was taken by 50 % (168/338). There was no significant association between a higher dose (>300 mg/day) and an increased risk of severe cutaneous manifestations [odds ratio (OR) 1.76; 95 % CI 0.73-4.22; p = 0.23]. Approximately 90 % (489/538) of patients developed AH within 60 days of initiating allopurinol therapy. Serum oxypurinol (the active metabolite of allopurinol) concentration was only recorded in six patients, four of whom had levels within the putative therapeutic range of 30-100 µmol/L. The HLA-B*5801 allele was present in 99 % (166/167) of patients tested, with the majority (147/166) being of Asian ancestry. The all-cause mortality rate was 14 % (109/788) with 94 AH-related deaths, all of which occurred in the cohort meeting the Singer and Wallace criteria. LIMITATIONS: The publications included in this review utilized different laboratory reference ranges to classify the non-cutaneous manifestations of AH; this may have introduced some variation in the cases identified as AH. A majority of the articles included in this analysis consisted of case reports and series--publication types that are not recognized as best-quality evidence; this thus limited the conclusions we could draw about the many risk factors we were interested in evaluating. CONCLUSIONS: Risk factors associated with AH, such as concomitant diuretic use, pre-existing renal impairment and recent initiation of allopurinol, were commonly present in AH patients; however, their role in the mechanism of AH remains to be established. A clear risk factor was the HLA-B*5801 status; this was especially relevant in Asian populations where there is a higher carriage rate of the allele. High allopurinol dose, previously suggested to be a risk factor, was not confirmed as such. The paucity of well-documented case reports and studies of AH render it difficult to draw more concrete conclusions or construct a meticulous profile of patients at risk of AH. Future case reports of AH need to be better documented to contribute to understanding the risks for, and mechanisms of, AH.

Understanding the dose-response relationship of allopurinol: predicting the optimal dosage.

AIMS: The aim of the study was to identify and quantify factors that control the plasma concentrations of urate during allopurinol treatment and to predict optimal doses of allopurinol. METHODS: Plasma concentrations of urate and creatinine (112 samples, 46 patients) before and during treatment with various doses of allopurinol (50-600 mg daily) were monitored. Non-linear and multiple linear regression equations were used to examine the relationships between allopurinol dose (D), creatinine clearance (CLcr) and plasma concentrations of urate before (UP) and during treatment with allopurinol (UT). RESULTS: Plasma concentrations of urate achieved during allopurinol therapy were dependent on the daily dose of allopurinol and the plasma concentration of urate pre-treatment. The non-linear equation: UT = (1 - D/(ID50 + D)) × (UP - UR) + UR , fitted the data well (r(2) = 0.74, P < 0.0001). The parameters and their best fit values were: daily dose of allopurinol reducing the inhibitable plasma urate by 50% (ID50 = 226 mg, 95% CI 167, 303 mg), apparent resistant plasma urate (UR = 0.20 mmol l(-1), 95 % CI 0.14, 0.25 mmol l(-1)). Incorporation of CLcr did not significantly improve the fit (P = 0.09). CONCLUSIONS: A high baseline plasma urate concentration requires a high dose of allopurinol to reduce plasma urate below recommended concentrations. This dose is dependent on only the pre-treatment plasma urate concentration and is not influenced by CLcr .

Fractional clearance of urate: validation of measurement in spot-urine samples in healthy subjects and gouty patients.

INTRODUCTION: Hyperuricemia is the greatest risk factor for gout and is caused by an overproduction and/or inefficient renal clearance of urate. The fractional renal clearance of urate (FCU, renal clearance of urate/renal clearance of creatinine) has been proposed as a tool to identify subjects who manifest inefficient clearance of urate. The aim of the present studies was to validate the measurement of FCU by using spot-urine samples as a reliable indicator of the efficiency of the kidney to remove urate and to explore its distribution in healthy subjects and gouty patients. METHODS: Timed (spot, 2-hour, 4-hour, 6-hour, 12-hour, and 24-hour) urine collections were used to derive FCU in 12 healthy subjects. FCUs from spot-urine samples were then determined in 13 healthy subjects twice a day, repeated on 3 nonconsecutive days. The effect of allopurinol, probenecid, and the combination on FCU was explored in 11 healthy subjects. FCU was determined in 36 patients with gout being treated with allopurinol. The distribution of FCU was examined in 118 healthy subjects and compared with that from the 36 patients with gout. RESULTS: No substantive or statistically significant differences were observed between the FCUs derived from spot and 24-hour urine collections. Coefficients of variation (CVs) were both 28%. No significant variation in the spot FCU was obtained either within or between days, with mean intrasubject CV of 16.4%. FCU increased with probenecid (P < 0.05), whereas allopurinol did not change the FCU in healthy or gouty subjects. FCUs of patients with gout were lower than the FCUs of healthy subjects (4.8% versus 6.9%; P < 0.0001). CONCLUSIONS: The present studies indicate that the spot-FCU is a convenient, valid, and reliable indicator of the efficiency of the kidney in removing urate from the blood and thus from tissues. Spot-FCU determinations may provide useful correlates in studies investigating molecular mechanisms underpinning the observed range of efficiencies of the kidneys in clearing urate from the blood. TRIAL REGISTRATION: ACTRN12611000743965.

Successful use of allopurinol in a patient on dialysis.

We report the case of a man with chronic tophaceous gout who had end-stage renal failure secondary to the Alport syndrome. Following a failed kidney transplant, where urate deposition was a suspected contributor, the patient responded positively to consistent allopurinol therapy and regular haemodialysis sessions. Extensive and destructive tophi receded in size remarkably and the almost constant incidence of acute attacks of gout subsided. The patient has recently received a new kidney transplant and his plasma concentrations of urate are controlled well with allopurinol and he no longer experiences acute attacks of gout. While efficacious, adherence is critical for achieving the therapeutic effects of allopurinol even in end-stage renal disease.