Utilization of allopurinol in the Australian community

An evaluation of gout visits in the United States for the years 2007 to 2011

Background

This study analyzed visits for and factors associated with gout and gout medication treatment trends for the years 2007–2011 in the United States given the introduction of febuxostat, the first new treatment option for gout in over 40 years, which was introduced to the market in 2009.

Methods

This study was a retrospective, cross-sectional, observational study of patients age 20 and older seen by providers who participated in the National Ambulatory Medical Care Survey (NAMCS), the National Hospital Ambulatory Medical Care Survey Outpatient Department (NHAMCS-OPD) or Emergency Department (NHAMCS-ED) in the United States. The outcome of interest was visits for gout diagnosis and visits where a gout medication was prescribed.

Results

Approximately 1.2% of visits had a diagnosis of gout. There was a significant increase in the percentage of visits with a diagnosis of gout in years 2009–2011 compared to 2007–2008, which remained after adjusting for covariates of interest. Groups more likely to have a visit with gout included those ≥65 and 45–64 (both as compared to those 20–44), the African-American and ‘Other’ race groups (as compared to Caucasians) and those on a diuretic. Groups less likely to have a visit with gout included females, Hispanic/Latinos, those with insurance type of ‘Other’ and Medicaid (both as compared to private insurance) and visits to a hospital emergency setting (as compared to physician’s office visits).

Conclusion

Although there was a significant increase in visits where gout is diagnosed across study years, the overall percentage of visits with a gout diagnosis is low in the US population. Treatment trends over the study years has remained consistent, with the introduction of febuxostat appearing to have little impact for the study years through 2011.

Gout prevalence and predictors of urate-lowering therapy use: results from a population-based study

Background

Gout has an increasing global prevalence. Underutilization of urate-lowering therapy (ULT) is thought to be common, via both suboptimal dosing and poor medication adherence. The aims of this study were to determine the prevalence of self-reported gout and the key predictors of ULT use in those with gout in a representative population survey in South Australia.

Methods

Data were obtained from the Spring 2015 South Australian Health Omnibus Survey, a multilevel, systematic, survey in a representative population sample involving face-to-face interviews (n = 3005). This study analyzed responses from respondents aged ≥ 25 years (n = 2531) about self-reported gout, ULT use, sociodemographic factors, lifestyle factors, and comorbidities, using survey weighting. Univariate and subsequent adjusted logistic regression analyses on self-reported gout were performed. ULT use was divided into three categories (never use, prior use, and current use) and these data were analyzed using a multinomial logistic regression model.

Results

Self-reported gout prevalence was 6.8% (95% CI 5.8, 7.9). The mean age of respondents with gout was 64 years (standard deviation 16) and 82% were male. As expected, older age, male gender, lower socioeconomic status (SES), and higher body mass index (BMI) were associated with gout, as were high alcohol consumption, current smoking, other forms of arthritis, and hypertension or hypercholesterolemia medication, after adjustment for sociodemographic variables. Two thirds of respondents with gout reported ULT use (36% current; 29% previous) with only 55% continuing treatment. Predictors of ULT use included male gender, low SES, and concomitant cholesterol-lowering therapy. Respondents with gout with a higher BMI were more likely to remain on ULT.

Conclusions

Despite gout being a common, potentially disabling joint disease, only 55% of respondents with gout in this study adhered to ULT. Identification of key predictors of ULT use will provide guidance on prescribing strategy in clinical practice and on the quality of gout care in the community.

Electronic supplementary material

The online version of this article (10.1186/s13075-018-1633-9) contains supplementary material, which is available to authorized users.

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.

The history and future of probenecid

Probenecid was initially developed with the goal of reducing the renal excretion of antibiotics, specifically penicillin. It is still used for its uricosuric properties in the treatment in gout, but its clinical relevance has sharply fallen and is rarely used today for either. Interestingly, throughout the last 60 years, there have been a host of apparently unrelated studies using probenecid in the clinical and basic research arena, including its potential use in the diagnosis and treatment of depression and its use to prevent fura-2 leakage in calcium transient studies. Recently, it has been shown that it is also an agonist of the Transient Receptor Potential Vanilloid 2 channel. Due to its unique action and new findings implicating TRPV channels in physiology and in disease, probenecid may have a new future as a research tool, and perhaps as a clinical agent in the neurology and cardiology fields. We review the history of probenecid in this paper and its potential future uses.

The epidemiology and treatment of gout

The development and expression of gout depends on three key steps: (1) chronic hyperuricemia, (2) the growth of monosodium urate (MSU) crystals, and (3) interaction between MSU crystals and the inflammatory system. Epidemiological studies have continued to improve our understanding of the environmental and genetic factors which influence chronic hyperuricemia and gout. The influence of obesity, alcohol, race, sex, age, and specific dietary components will be discussed below. The primary mechanism of hyperuricemia is insufficient renal clearance of uric acid which in turn is dependent on transport of uric acid in the proximal renal tubule. Knowledge of the transport mechanisms has improved understanding of the genetic influences on gout and is relevant to understanding of the effects of drugs which can increase or decrease renal uric acid clearance. The application of established principles of management including diagnosis through crystal identification, the gradual introduction of hypouricemic therapy with the use of prophylaxis to reduce the risk of flares, identification of a suitably low target of plasma urate, a progressive increase in therapy to achieve the target and taking steps to encourage good compliance, has the potential to improve outcomes for patients with this very common affliction. The potential role for new therapies will also be discussed.

Management of gout: beyond allopurinol

The basic concepts of the pathogenesis and management of gout have not altered for many years. Monosodium urate monohydrate crystals drive the disease and identification of these crystals is required for certain diagnosis. In contrast, our understanding of the mediators of gouty inflammation, the appropriate target serum urate concentration during treatment, the drugs available and the best ways to use those drugs have all advanced in recent years and will be the focus of this review.

A benefit-risk assessment of benzbromarone in the treatment of gout. Was its withdrawal from the market in the best interest of patients?

Benzbromarone, a potent uricosuric drug, was introduced in the 1970s and was viewed as having few associated serious adverse reactions. It was registered in about 20 countries throughout Asia, South America and Europe. In 2003, the drug was withdrawn by Sanofi-Synthélabo, after reports of serious hepatotoxicity, although it is still marketed in several countries by other drug companies. The withdrawal has greatly limited its availability around the world, and increased difficulty in accessing it in other countries where it has never been available.The overall aim of this paper is to determine if the withdrawal of benzbromarone was in the best interests of gouty patients and to present a benefit-risk assessment of benzbromarone. To determine this, we examined (i) the clinical benefits associated with benzbromarone treatment and compared them with the success of alternative therapies such as allopurinol and probenecid, particularly in patients with renal impairment; (ii) the attribution of the reported cases of hepatotoxicity to treatment with benzbromarone; (iii) the incidence of hepatotoxicity possibly due to benzbromarone; (iv) adverse reactions to allopurinol and probenecid. From these analyses, we present recommendations on the use of benzbromarone.Large reductions in plasma urate concentrations in patients with hyperuricaemia are achieved with benzbromarone and most patients normalize their plasma urate. The half-life of benzbromarone is generally short (about 3 hours); however, a uricosuric metabolite, 6-hydroxybenzbromarone, has a much longer half-life (up to 30 hours) and is the major species responsible for the uricosuric activity of benzbromarone, although its metabolism by cytochrome P450 (CYP) 2C9 in the liver may vary between patients as a result of polymorphisms in this enzyme. It is effective in patients with moderate renal impairment. Standard dosages of benzbromarone (100 mg/day) tend to produce greater hypouricaemic effects than standard doses of allopourinol (300 mg/day) or probenecid (1000 mg/day).Adverse effects associated with benzbromarone are relatively infrequent, but potentially severe. Four cases of benzbromarone-induced hepatotoxicity were identified from the literature. Eleven cases have been reported by Sanofi-Synthélabo, but details are not available in the public domain. Only one of the four published cases demonstrated a clear relationship between the drug and liver injury as demonstrated by rechallenge. The other three cases lacked incontrovertible evidence to support a diagnosis of benzbromarone-induced hepatotoxicity. If all the reported cases are assumed to be due to benzbromarone, the estimated risk of hepatotoxicity in Europe was approximately 1 in 17 000 patients but may be higher in Japan.Benzbromarone is also an inhibitor of CYP2C9 and so may be involved in drug interactions with drugs dependent on this enzyme for clearance, such as warfarin. Alternative drugs to benzbromarone have significant adverse reactions. Allopurinol is associated with rare life-threatening hypersensitivity syndromes; the risk of these reactions is approximately 1 in 56 000. Rash occurs in approximately 2% of patients taking allopurinol and usually leads to cessation of prescription of the drug. Probenecid has also been associated with life-threatening reactions in a very small number of case reports, but it frequently interacts with many renally excreted drugs. Febuxostat is a new xanthine oxidoreductase inhibitor, which is still in clinical trials, but abnormal liver function is the most commonly reported adverse reaction.Even assuming a causal relationship between benzbromarone and hepatotoxicity in the identified cases, benefit-risk assessment based on total exposure to the drug does not support the decision by the drug company to withdraw benzbromarone from the market given the paucity of alternative options. It is likely that the risks of hepatotoxicity could be ameliorated by employing a graded dosage increase, together with regular monitoring of liver function. Determination of CYP2C9 status and consideration of potential interactions through inhibition of this enzyme should be considered. The case for wider and easier availability of benzbromarone for treating selected cases of gout is compelling, particularly for patients in whom allopurinol produces insufficient response or toxicity.We conclude that the withdrawal of benzbromarone was not in the best interest of patients with gout.