AST-120 in Hemodialysis Patients With Uremic Pruritus

Uremic toxins, such as indoxyl sulfate (IS) and p-cresol, or p-cresyl sulfate (PCS), are markedly accumulated in the organs of chronic kidney disease (CKD) patients. These toxins can induce inflammatory reactions and enhance oxidative stress, prompting glomerular sclerosis and interstitial fibrosis, to aggravate the decline of renal function. Consequently, uremic toxins play an important role in the worsening of renal and cardiovascular functions. Furthermore, they destroy the quantity and quality of bone. Oral sorbent AST-120 reduces serum levels of uremic toxins in CKD patients by adsorbing the precursors of IS and PCS generated by amino acid metabolism in the intestine. Accordingly, AST-120 decreases the serum IS levels and reduces the production of reactive oxygen species by endothelial cells, to impede the subsequent oxidative stress. This slows the progression of cardiovascular and renal diseases and improves bone metabolism in CKD patients. Although large-scale studies showed no obvious benefits from adding AST-120 to the standard therapy for CKD patients, subsequent sporadic studies may support its use.

Pruritus is a common and distressing symptom that affects patients with chronic kidney disease (CKD). Indoxyl sulfate (IS) and p-cresyl sulfate (PCS) are uremic toxins with similar protein binding, dialytic clearance, and proinflammatory features. The pathogenesis of uremic pruritus is not well elucidated, although it is theorized that inflammation may play a role. Elevated levels of C-reactive protein (CRP), interleukin-6, and interleukin-2 have been found among patients on hemodialysis suffering from pruritus, which may also partly explain the association the investigators found between low hemoglobin levels and a higher prevalence of pruritus, given the association between low hemoglobin and inflammatory states. Since the pathophysiology of uremic pruritus is multifactorial. Subclinical or overt uremic neuropathy, skin or nerve inflammation in the context of kidney failure-associated chronic systemic inflammation, or an increase in activity of μ-opioid receptors due to kidney failure have all been implicated.

A large, international study demonstrated the prevalence of moderate-to-extreme pruritus among patients with end-stage kidney disease on hemodialysis to be approximately 40% and was associated with a higher prevalence of comorbid conditions, worse biochemical profiles, poorer mental and physical quality of life, a higher probability of depression, and poorer sleep quality and survival. More recently, this prevalence was shown to range from 26% in Germany to 48% in the United Kingdom. Other studies have also demonstrated an association between pruritus and worse kidney disease burden scores, poorer health-related quality of life, and greater frequency of sleep disturbances in patients on dialysis.

However, pruritus is often overlooked by health care providers within dialysis units. In dialysis facilities where 21%-50% of patients reported having severe pruritus, only 1% of medical directors estimated this same prevalence. This may be due, in part, to underreporting by patients, as 17% of patients who were nearly always or always bothered by pruritus had not reported their symptoms to any health care provider.

Uremic pruritus intensity is also associated with multiple health-related quality-of-life outcomes, such as sleep quality, mood, and social function, and is independently associated with mortality. Uremic pruritus has been identified as a key research priority by patients with kidney disease.

Although several small studies have examined a variety of interventions, the efficacy of these interventions and the optimal treatments remain poorly defined. To address this important knowledge gap, the investigators systematically reviewed the literature and summarized the evidence for the major interventions for the treatment of uremic pruritus. The investigators will choose AST-120 as therapeutic agents for uremic pruritus.