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Aluminum Overload: Aluminum overload is most commonly seen in patients with renal failure who must undergo dialysis. Aluminum can be present in the water used to prepare dialysate and in aluminum-containing phosphate binders, and can cause adverse effects on bone, the hematopoietic system, and the brain. Desferal may be used for treatment of aluminum overload.
Mercury poisoning: Chelation therapy has been proposed to treat metal toxicity from dental amalgam fillings, but it has not been shown that mercury amalgams cause harm to patients with dental fillings, except in rare cases of allergy.
Chelation Therapy for Non-Overload Conditions: Chelation therapy has been proposed as a treatment for a variety of non-overload conditions in which the removal of heavy metal ions is hypothesized to reduce oxidative damage caused by the production of hydroxyl radicals. However, the possible mechanism of chelators as therapeutic agents for nonoverload conditions is not fully understood. Chelation has been investigated as a treatment of numerous non-overload conditions including, but not limited to, cardiovascular disease, rheumatoid arthritis, cancer, and diabetes.
Research Chelation Therapy for Overload Conditions The majority of the studies available for review were relatively small, uncontrolled studies, although some of the studies evaluating chelation therapy for lead overload were placebo-controlled randomized trials. Most of the studies addressed the use of chelating agents for iron overload in thalassemia patients and for lead toxicity in children with environmental exposure to lead. There was very little research regarding the use of copper chelators for patients with Wilson's disease and also very little data regarding treatment of aluminum overload in patients receiving chronic dialysis. With the exception of some of the iron overload studies, few of these studies provided long-term follow-up.
Iron Overload: Studies evaluating the use of chelation therapy for iron overload in thalassemia patients were largely uncontrolled, with heterogeneity in treatment protocols and patient characteristics. A number of the studies used intravenous deferoxamine (DFO), the chelation therapy approved by the U.S. Food and Drug Administration (FDA) and currently considered standard of care for treatment of iron overload. Results of these studies suggest that early treatment with DFO may reduce the risk of heart disease and other complications, and several studies documented long-term survival in patients who had received DFO for a number of years. (Olivieri, 1995; Richardson, 1993; Olivieri, 1994) In a phase 3 study, patients with beta-thalassemia were randomized to receive deferasirox (n=296) or deferoxamine (n=290).
(Cappellini, 2006) Both groups had significant dose dependent reductions in liver iron concentration and serum ferritin.
Several other studies evaluated the use of deferiprone, an oral iron-chelating agent that has been given orphan drug status by the FDA. To evaluate the effectiveness of oral deferiprone, Addis et al. (1999) conducted a meta-analysis of the medical literature published between 1989 and 1996.The investigators concluded that deferiprone can achieve negative iron balance and reduce body iron burden in highly iron-overloaded patients. However, the evidence was insufficient to
Chelation Therapy - Commercial Medical Management Guideline
determine whether oral deferiprone therapy resulted in increased survival. A literature review by Caro et al. (2002) evaluated studies published between 1966 and 1999 that compared subcutaneous desferrioxamine with oral deferiprone;
this review included 8 studies, and found that desferrioxamine was more effective than deferiprone in lowering hepatic iron concentration.
Lead Overload: Findings in the available studies that investigated the efficacy of the lead chelators, ethylenediamine tetraacetic acid (EDTA) and Meso 2,3-dimercaptosuccinic acid (DMSA) were mixed. A randomized, controlled trial by Lin et al. (1999) found that EDTA may slow progression of renal insufficiency in adult patients with lead overload.
Chisolm (2000) performed an open-label study of DMSA in children, reporting that urinary lead excretion increased substantially during the first 8 hours of treatment, and average blood lead decreased to 58% of the average pretreatment blood lead level. Two placebo-controlled, double-blind, randomized, controlled trials failed to find a significant effect of DMSA on blood lead levels in children with blood lead levels between 20 and 45 mg/dL, (O'Connor, 1999; Rogan, 2001) and two studies reported no effect of EDTA on lead levels in children. (Markowitz, 1993, Rosen, 1993) Additional larger studies will be required to confirm these findings; most of the available studies involved relatively small study populations, and therefore may have lacked sufficient statistical power to detect a moderate treatment effect. None of the studies documented an effect of chelation therapy on neurobehavioral deficits caused by lead toxicity.
Dietrich et al. (2004) evaluated the effect of chelation therapy in a study of 780 children with blood lead levels between 20 and 44 mg/dL who were randomized to chelation therapy or a placebo group. Chelation therapy lowered blood lead level for approximately 6 months but resulted in no cognitive, behavior, or neuromotor benefits. The investigators concluded that chelation therapy cannot be recommended for children with blood lead levels below 45 mg/dL.
Lin-Tan et al. (2007) evaluated 116 non-diabetic patients with chronic kidney diseases, high-normal body lead burden (BLB), and no lead exposure history who were randomly assigned to a chelation or control group in a 4-year clinical trial. The 58 chelation group patients received lead-chelation therapy with calcium disodium EDTA, and the 58 control group patients received placebos. The investigators concluded that repeated chelation therapies can, over a four-year period, slow progression of renal insufficiency in non-DM patients with high-normal BLB.
Copper Overload: Despite the fact that chelation therapy is a mainstay of treatment for patients with Wilson's disease, the literature search for studies of chelation therapy for copper toxicity yielded only a few small case series with extremely small patient populations (less than 10) and a single large study (n=137). This single study was a retrospective case series that reported on patients with neurological Wilson's disease who had been treated with a variety of chelating agents, including oral penicillamine, trientine, molybdate, and/or zinc acetate in patients with copper toxicity due to Wilson's disease. Nine patients in the study had received little or no treatment. The response to treatment was classified as excellent in 57 patients, good but with some minor neurological problems in 36 patients, and poor in 24 patients. There were also 20 deaths; all 9 untreated patients died, along with 11 patients who had apparently been adequately treated. The authors reported that no obvious cause of death was found in these patients, and noted that adequate chelation failed to lower brain and/or liver copper levels in some patients. (Walshe, 1993) Aluminum Overload: Few published studies have investigated chelation for the treatment of patients with aluminum overload. Roger et al. (1991) investigated the use of DFO in hemodialysis patients administered human recombinant erythropoietin (r-HuEPO). R-HuEPO is utilized to stimulate red blood cell production in transfusion-dependent hemodialysis patients. Due to serious complications that developed in a large percentage of this small study population, the authors concluded that DFO administered in conjunction with r-HuEPO was unsafe.
A study conducted by Barata et al. (1996) reported lowered serum aluminum in DFO-treated dialysis patients. However, this study is limited by lack of controls and a small study population. Additionally, it was not determined whether lowered serum aluminum levels increased long-term survival rates in dialysis patients.
Chelation Therapy - Commercial Medical Management Guideline Mercury poisoning: Randomized controlled trials have concluded that mercury amalgams used in dental restorations cause no harm to patients. (Bellinger, 2006; DeRouen, 2006) Professional Organizations American Academy of Pediatrics (AAP): In 2005, the AAP released a policy statement for lead exposure in children.
(American Academy of Pediatarics, 2005) Treatment recommendations were issued according to the patient's blood lead
level as follows:
- 10 mg/dL to 44 mg/dL: Lead education and environmental and medical evaluation are recommended. Chelation therapy is not indicated.
- 45 mg/dL to 69 mg/dL: Chelation therapy is recommended in addition to environmental and medical evaluation.
- 70 mg/dL or more: Inpatient chelation therapy is indicated.
The AAP policy statement on aluminum toxicity in infants and children states that there is some evidence to support the use of intravenous deferoxamine to treat aluminum toxicity in children. However, the statement goes on to caution that deferoxamine therapy is not without hazards, and has been associated with a number of adverse events, such as allergic reactions, including pruritus, wheals, and anaphylaxis, dysuria, abdominal discomfort, diarrhea, fever, leg cramps, tachycardia, cataracts, and neurotoxicity. (American Academy of Pediatrics, 1996) Chelation Therapy for Non-Overload Conditions Well-designed, published and peer-reviewed studies do not support chelation treatment for chronic, progressive diseases such as cardiovascular disease, atherosclerosis, diabetes, cancer, Alzheimer's disease, autism spectrum disorder, or rheumatoid arthritis. There are no studies available regarding chelation therapy for the treatment of apoplectic coma, chronic fatigue syndrome, chronic renal insufficiency, defective hearing, diabetic ulcer, cholelithiasis, gout, erectile dysfunction, multiple sclerosis, osteoarthritis, osteoporosis, Parkinson's disease, Raynaud's disease, renal calculus, schizophrenia, scleroderma, snake venom poisoning, varicose veins, or vision disorders.
Cardiovascular disease: Knudtson et al. (2002) conducted a double-blind, randomized controlled study of EDTA for the treatment of ischemic heart disease. A total of 84 patients were randomized to receive 33 infusions of EDTA (n=41) or placebo (n=43) solution. At 27 weeks, both groups significantly increased the exercise time to ischemia. There were no differences between the groups for any outcome measures or in the number of clinical ischemic events. These results indicate that EDTA treatment had no beneficial effect on ischemic heart disease. However, the study patients had mild disease, the results may not be representative of patients with more severe disease, and an effect of the vitamins and minerals in the infusion solution cannot be ruled out.
In a sub-study of the Knudtson et al. study, Anderson et al. (2003) conducted a double-blind, randomized controlled study to ascertain the effects of EDTA on endothelial function in patients with ischemic heart disease. A total of 47 patients were randomized to receive 33 infusions of EDTA (n=24) or placebo (n=23) solution. At 6 months posttreatment, the infusions had no significant effect on brachial artery diameter, flow-mediated vasodilation, or nitroglycerin-mediated vasodilation for either group. The results suggest that EDTA therapy had no effect on brachial artery diameter in patients with CAD. This study is flawed by a small sample size.
In a systematic review of 7 articles assessing EDTA chelation therapy for cardiovascular disease, Seely et al. concluded that the best available evidence does not support the use of EDTA chelation for cardiovascular disease. (Seely, 2005) Anthracycline-Associated Cardiac Toxicity in Breast Cancer Patients: Two studies, one a randomized controlled trial (Speyer, 1988) and the other a multicenter uncontrolled study (Kolaric, 1995), assessed chelation therapy for anthracycline-associated cardiac toxicity. Both studies reported a significant cardioprotective effect of dexrazoxane on anthracycline-induced toxicity. However, definitive conclusions regarding the benefits of dexrazoxane cannot be made since there was no long-term follow-up in either study and therefore, it is unknown whether chelation therapy had a Chelation Therapy - Commercial Medical Management Guideline positive impact on survival.
Rheumatoid Arthritis: In a review of chelation for non-overload conditions, Voest et al. summarized the available literature regarding rheumatoid arthritis (Voest, 1994). In six small studies with patient populations ranging from 6 to 18 patients, deferoxamine improved the clinical symptoms of arthritis and reduced anemia in the majority of patients.
However, the authors concede that the preponderance of evidence regarding chelation for rheumatoid arthritis is derived from small numbers of patients treated for a short amount of time. The authors assert that larger studies are needed to determine the role of iron chelators in the treatment of rheumatoid arthritis. In a second review, Ghio et al. (1997) hypothesized that iron chelation may play a vital role in reducing neutrophilic inflammation. Thus, these investigators also contend that additional trials of iron chelation for rheumatoid arthritis are warranted.
Alzheimer's Disease: Several studies have reported some improvement in cognitive function or slowing of the rate of decline in patients treated with clioquinol or deferoxamine (Crapper Mclachlan, 1991; Regland, 2001; Ritchie, 2003).
However, these studies were small, only two were placebo-controlled, and none were double-blind, and therefore no conclusions regarding efficacy of chelation therapy for Alzheimer's disease can be made on the basis of these studies.