What Is DMPS and Its Role in Heavy Metal Chelation?

The compound 2,3-Dimercapto-1-propanesulfonic acid, or DMPS, is a synthetic chemical also known by its sodium salt form, Unithiol. It is classified as a chelating agent, which means it has the capacity to bind with various heavy metals. First synthesized in 1956, this compound is structurally related to another chelating agent, dimercaprol. Its primary role in medicine is as an antidote for heavy metal poisoning.

Primary Uses of DMPS

DMPS is most recognized for its effectiveness in addressing mercury poisoning. Studies have shown that DMPS can lower the total amount of mercury in the body and help reduce urinary mercury levels back to a normal range, particularly in cases of exposure to mercurous chloride. The compound is also utilized in cases of arsenic poisoning, where it helps facilitate the removal of the toxic metal from the body.

Beyond mercury and arsenic, DMPS is sometimes considered for lead poisoning. The decision to use DMPS is based on confirmed, significant heavy metal exposure, often determined through laboratory testing of blood or urine. The therapy is intended to mitigate the toxic effects of these metals and reduce the overall body burden.

DMPS has also been investigated for its effects against poisoning by other elements, such as polonium-210. Early research indicated it could offer some protective benefit and prolong survival time following exposure.

How DMPS Functions in the Body

The therapeutic action of DMPS is centered on chelation, a chemical process that involves the binding of the DMPS molecule to heavy metal ions in the bloodstream and tissues. The DMPS molecule possesses specific chemical structures called sulfhydryl groups, which contain sulfur and hydrogen atoms. These groups have a strong affinity for heavy metals and act like claws, grabbing onto the metal ions.

Once DMPS binds to a heavy metal ion, such as mercury or arsenic, it forms a new, stable, water-soluble compound. This newly formed complex is chemically different from the original metal ion, which is often poorly soluble and can become lodged in tissues. The water-soluble nature of the DMPS-metal complex allows it to be mobilized and transported through the bloodstream.

The body’s primary filtration system, the kidneys, can then easily filter this water-soluble complex from the blood. After filtration, the complex is passed into the urine and expelled from the body. This mechanism reduces the overall toxic load and prevents further damage.

Administration Routes and Side Effects

DMPS is administered to patients either through an intravenous (IV) injection or infusion, or as an oral capsule. The choice of administration route, along with the specific dosage and treatment duration, is determined by a healthcare professional. These decisions are based on factors like the type and severity of the heavy metal poisoning, as well as the patient’s overall health and body weight.

Patients undergoing treatment with DMPS may experience a range of side effects. Common reactions can include skin issues such as rashes or itching at the injection site, as well as gastrointestinal disturbances like nausea or diarrhea. Some individuals might also feel dizzy or experience a temporary drop in blood pressure following administration.

While many side effects are mild and transient, more serious adverse events can occur, although they are less common. There have been rare reports of severe allergic reactions or significant skin conditions like Stevens-Johnson syndrome.

Important Considerations and Regulatory Landscape

The regulatory status of DMPS varies by country. In some European nations, it is an approved medication for treating heavy metal poisoning. In the United States, DMPS is not broadly approved by the Food and Drug Administration (FDA). Instead, it is available through compounding pharmacies, which can prepare it for specific patient needs under the direction of a licensed practitioner.

Due to its potent effects, DMPS should only be used under the guidance of a qualified healthcare professional with experience in chelation therapy. There are specific situations where its use may not be appropriate, such as in individuals with severe kidney disease, as the kidneys are responsible for excreting the DMPS-metal complexes. A known allergy to DMPS or other sulfur-containing compounds is another contraindication.

A consideration during therapy is that DMPS is not exclusively selective for toxic heavy metals. It can also bind to and promote the excretion of essential minerals like zinc and copper. Therefore, medical providers often monitor the levels of these minerals in the body during treatment and may recommend supplementation to prevent deficiencies.