Tighter restrictions are being placed on the sale of DMSA and possibly other compounds used to do challenge testing of urine for toxic elements.  This will make it more difficult to do the challenged urine testing that has come to be a favored way of assessing a patient’s body burden of toxic elements like mercury. Thus, the controversial topic of chelating agents for testing or therapy is raised again.
 

Ever since I heard the impassioned presentations by Ray Evers, M.D. nearly 40 years ago, I have marveled at the apparent clinical potential for i.v. EDTA therapy.  Dripping the sodium salt of a potent divalent metal chelator into the blood stream shifts the ionic equlibria. The dynamic flux of magnesium, calcium, zinc, lead, etc. changes according to how each metal ion shifts its affinity from protein binding sites to the circulating EDTA. Other than that, we know very little about physiological mechanism that might lead to benefit from such therapy. Use of i.v. EDTA has long been an approved treatment for acute toxic metal poisoning, so, if toxic levels of a metal can be demonstrated, then the treatment is warranted.

Shifting the tissue status of ionic calcium, magnesium and other elements can have profound effects on multiple ion-dependent pathways. It is very possible that those shifts are the predominant cause of symptom improvements in a given patient who is treated with metal-binding agents rather than any reduction of toxic element concentrations. Certainly those shifts are the origin of unfortunate events from miss-applications of chelating agents.

The initial notion of direct plaque removing by the use of i.v. EDTA has fallen into disfavor, and we still have little knowledge about how improvements in signs and symptoms may come about. Putting cures for atherosclerosis aside, we are left with the initial reason for clinical use of chelating agents: acute metal toxicity. And that leads us to the central question regarding low level chronic exposures to toxic elements. How do you know when such exposure is producing a clinical effect that warrants aggressive toxic element removal interventions?

Chronic exposures to elevated levels of toxic elements have many well-documented clinical effects from large population studies. Translating that evidence to clinical practice, however, is tricky. How do you know if chronic, low-level exposure is causing any specific symptom or sign in a given patient? Proceeding to treat based on evidence of simple upper-range levels in body fluids or hair may create side effects and involve unnecessary costs because exposure does not predicate clinical effect. That is why evidence of some toxic functional effect is so valuable.

Looking for abnormalities in a urinary porphyrin profile is one of (if not the best) way to check for metabolic effects due to toxic element exposure. And when such effects are found, then the level of exposure is not the central issue. Monitoring levels is useful to discover which toxicant is most prevalent at each stage of treatment and for evaluating the effectiveness of treatment for moving toxic elements into urine. But the focus of treatment is to cause normalization of porphyrin pathway issues.

So, a porphyrin profile is the best guide for therapy. Porphyrin profiling is:

• Proven (see Laboratory Evaluation for Integrative and Functional Medicine, Ch 8)
• Able to discriminate among  types of toxicants (esp. mercury)
• Consistent with multiple lines of evidence about toxic effects
• Involves no challenge substance or potential for false positives due to exogenous specimen contamination

Nay-sayers may fear that their presumptions about very wide-spread clinical effects from low-level toxic element exposure will need re-investigation. They do need investigation. Particularly, the following needs experimental confirmation in humans:      Hypothesis: Except in cases of acute toxic exposure, finding elevated levels of ____________ (mercury or other metal) in a patient’s body fluids or hair is a reliable predictor of _____________ (fill in the symptom). (Epidemiological and animal evidence is NOT adequate.)

Finding elevated levels of toxic metals by any of the current tests is of considerable clinical value for detecting exposures that should be reduced. The question is one of clinical imperative for using aggressive procedures with potential adverse side effects to rapidly bring tissue levels down. If there are no current toxic effects as shown by porphyrin profiling, then the safer approaches of changes in diet, occupation and lifestyle, along with mild supplemental agents to lower absorption (dietary fiber) and accumulation (competing nutrient elements) may be all that is needed.