What are the effects of oral adsorbents in delaying progression or preventing chronic kidney disease?

Chronic kidney disease (CKD) is a global public health problem. People with CKD are at high risk of cardiovascular events and kidney failure. Deterioration of kidney function causes an increase of uraemic toxin in blood, which in turn promotes CKD progression.

Oral adsorbents are a group of agents with ability to adsorb and remove uraemic toxin secreted and produced in the gastrointestinal tract and eliminated in faeces, which have been used in clinical practice to decrease kidney injury.

We included 15 studies which recruited 1590 participants in this review. Few studies reported on our primary outcomes of interest. Oral AST-120, Ai Xi Te and Niaoduqing granules may have beneficial effects on retarding the decline of kidney function with no serious adverse events for patients with CKD. These studies were methodologically low. Currently there is no strong evidence for recommending any oral adsorbents for preventing or delaying the progression for patients with CKD. More research is needed.

Authors' conclusions: 

Few studies reported our primary outcomes of interest. For our secondary outcomes, there is evidence of limited quality that AST-120, Ai Xi Te and Niaoduqing granules may have positive effects on delaying the decline of kidney function. There were no serious adverse events for any of the interventions in patients with CKD. Given the lack of information for our primary outcomes, the low methodological quality of most studies, and the small sample sizes, there is no strong evidence on the effectiveness of these oral adsorbents.

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Background: 

Chronic kidney disease (CKD) is a worldwide public health problem which is at high increased risk of cardiovascular disease (CVD) and renal failure. Deterioration of kidney function causes an increase in circulating toxins, which, in turn promotes the progression of CKD. Oral adsorbents with capacity to adsorb and remove substances including uraemic toxins from the intestine could be effective in minimising kidney injury.

Objectives: 

To investigate the benefits and harms of oral adsorbents for preventing or delaying the progression of CKD.

Search strategy: 

We searched the Cochrane Renal Group's Specialised Register (to 22 September 2014) through contact with the Trials' Search Co-ordinator using search terms relevant to this review. The following four Chinese medical databases were also searched: China Biological Medicine Database (1979 to May 2012); Chinese Science and Technique Journals Database (to May 2012); China National Infrastructure (to May 2012); Wan Fang database (to May 2012).

Selection criteria: 

Randomised controlled trials (RCTs) and quasi-RCTs comparing any oral adsorbents for preventing or delaying the progression of CKD.

Data collection and analysis: 

Two authors independently assessed and extracted information. Information was collected on methods, participants, interventions and outcomes (incidence of end-stage kidney disease (ESKD), mortality, quality of life and adverse events). Results were expressed as risk ratios (RR) for dichotomous outcomes or as mean differences (MD) for continuous data with 95% confidence intervals (CI). Adverse events were expressed as risk differences (RD).

Main results: 

Fifteen studies (1590 patients) conducted in Japan, China, and the USA were identified. The risk of bias of the included studies was moderate or high and the sample sizes were small.

Three studies compared oral AST-120 plus routine treatment with placebo plus routine treatment; however data on our outcome measures of interest were not reported in two studies. These studies did not assess or did not provide data for our primary outcomes of interest (incidence of ESKD; time to ESKD; all-cause mortality). There was no significant difference in the changes of serum creatinine (SCr), slope of 1/SCr over time and creatinine clearance (CrCl) between AST-120 and placebo for patients with CKD.

Eight studies compared oral AST-120 plus routine treatment with routine treatment alone; data on our outcome measures of interest were not reported in one study. There was no significant difference in incidence of ESKD, all-cause mortality and the change in health-related quality of life between AST-120 and routine treatment for patients with CKD. AST-120 showed beneficial effects on delaying the decline of kidney function measured by using the slope of change in estimated CrCl (SMD 0.39, 95% CI 0.21 to 0.5) and the mean changes of glomerular filtration rate (GFR) (MD -0.76 mL/min/mo, 95% CI -0.82 to -0.70) for patients with CKD; AST-120 was not superior to routine treatment in retarding the decline of kidney function measured by using the 1/SCr slope over time, occurrence of increase in SCr concentration, doubling of SCr concentration, changes in GFR from baseline (mL/min/1.73 m²) and slope of the eGFR curve (mL/min/mo) for patients with CKD.

Three studies compared oral Ai Xi Te plus routine treatment with routine treatment alone. These studies did not assess our primary outcomes of interest. Compared with routine treatment, Ai Xi Te had positive effects on reducing SCr (MD -113.40 (µmol/L), 95% CI -188.69 to -38.10) and retarding the decline of CrCl (MD 9.74 (mL/min), 95% CI 4.28 to 15.21) for patients with CKD.

One study compared oral Niaoduqing granules plus routine treatment with routine treatment alone, but did not assess our primary outcomes of interest. Compared with routine treatment, Niaoduqing granules had positive effects on reducing SCr (MD -135.60 (µmol/L), 95% CI -198.03 to -73.17) and CrCl (MD 13.30 (mL/min), 95% CI 5.69 to 20.91).

The most commonly reported adverse events associated with AST-120 and Ai Xi Te were gastrointestinal symptoms however no serious adverse events were reported.

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